Topic 1 Atoms, Molecules and Stoichiometry

The following are high-level thinking skills (KBAT) questions designed based on the learning outcomes provided:

1.1 Fundamental particles of an atom

– What is the symbol of fundamental subatomic particles?
Particle – Symbol – Mass
electron e- 0.0005486 amu
proton p+ 1.007276 amu
neutron no 1.008665 amu
– why do the nucleon number and the relative atomic mass of boron show different values?
the nucleon number refers to the exact number of proton plus neutron in the nucleus of the atom. The relative atomic mass is the average of the masses of the different isotopes, and taking into consideration of their relative abundance. 
– what is difference between nucleon number and mass number?
same. The mass number (A), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. The mass number is different for each differenxxt isotope of a chemical element.
– what is difference between nucleon number and relative atomic mass?
Atomic mass is the weighted average mass of an atom of an element based on the relative natural abundance of that element’s isotopes. The mass number is a count of the total number of protons and neutrons in an atom’s nucleus.
– What is the mass of a neutron?
The masses of the proton and neutron are quite similar: The proton is 1.6726×10−27 kg or 938.27 MeV/c2, while the neutron is 1.6749×10−27 kg or 939.57 MeV/c2.
– what is isoelectronic in chemistry?
When two elements and/or ions have the same electronic configurations it is said that they are “isoelectronic” with one another. When two chemical species are isolectronic they again tend to have similar chemical properties. Examples of Isoelectronic Elements and/or Ions. Element or ion pair.
– how do you calculate nucleons?
The total number of nucleons in a nucleus is usually denoted by the mass number A, where A = Z + N, Z protons and N neutrons. The chemical properties of an atom are determined by the number of electrons, the same as the number of protons Z. This is called the atomic number.
– are protons and neutrons nucleons?
“Nucleon” is the collective name for neutrons and protons. They are the particles that make up the atomic nucleus.
– why are protons and neutrons called nucleons?
Protons and Neutrons reside together in the Nucleus of the whole system. So, they are called Nucleons. Proton and neutron constitute the nucleus of the atom. So they are called as nucleons.
– What is the difference between nuclear charge and effective nuclear charge?
Nuclear charge is the total charge of a nucleus. (Proton is positively charge while neutron is neutral (don’t have charge). Effective nuclear charge is the net charge that an outermost shell electron experiences. The main difference between nuclear charge and effective nuclear charge is that the value of the effective nuclear charge is always a lower value than that of the nuclear charge.
– what is the relation between effective nuclear charge and shielding effect?
The shielding effect explains why valence-shell electrons are more easily removed from the atom. The effect also explains atomic size. The more shielding, the further the valence shell can spread out and the bigger atoms will be. The effective nuclear charge is the net positive charge experienced by valence electrons.
– which one is the heaviest particle?
The heaviest particle of an atom is its neutron. It is due to its weight difference from others. It is 0.18% heavier than the proton which makes it the most heaviest.
– which of the three subatomic particles is the heaviest?
Neutron is heaviest subatomic particle among the given subatomic particles with mass of 1.008 amu while proton have mass of 1 amu.
– what is the heaviest proton neutron or electron?
Atomic particles. Protons and neutrons have approximately the same mass. However, one proton is about 1,835 times more massive than an electron.

1.2 Relative atomic, isotopic, molecular and formula masses

– what is relative atomic mass and relative molecular mass?

– what is the difference between relative atomic mass and relative molecular mass?

– what is the formula of relative molecular mass?

Relative molecular mass = (number of atoms of element 1 × relative mass of element 1) + (number of atoms of element 2 × relative mass of element 2) + . You can use this same approach for any molecule.

 

– what is the difference between mass number and atomic relative mass?
Atomic mass is also known as atomic weight. Atomic mass is the weighted average mass of an atom of an element based on the relative natural abundance of that element’s isotopes. The mass number is a count of the total number of protons and neutrons in an atom’s nucleus.

– what is relative abundance of element?

The relative abundance of an isotope is the percentage of atoms with a specific atomic mass found in a naturally occurring sample of an element.

– what is mass spectrometer?

A mass spectrometer produces charged particles (ions) from the chemical substances that are to be analyzed. The mass spectrometer then uses electric and magnetic fields to measure the mass (“weight”) of the charged particles.

– what is a mass spectrum used for?
Mass spectrometry is an analytical tool useful for measuring the mass-to-charge ratio (m/z) of one or more molecules present in a sample. These measurements can often be used to calculate the exact molecular weight of the sample components as well.
– what is mass spectrometry?
Mass spectrometry is an analytical tool useful for measuring the mass-to-charge ratio (m/z) of one or more molecules present in a sample. These measurements can often be used to calculate the exact molecular weight of the sample components as well.
– why pressure is kept low in mass spectrometer?
It is important that a low pressure is maintained in the spectrometer so that the ions can pass through unhindered by molecules in the air. the need for a vacuum is important that the ions produced in the ionization chamber have a free run through the machine without hitting air molecules.
– what is m/e really meaning in mass spec?
The abbreviation m/z is used to denote the dimensionless quantity formed by dividing the mass number of an ion by its charge number. The abbreviation m/e is, therefore, not recommended.
– what is meaning tallest peak in mass spectrometry?
The base peak is the tallest peak because it represents the commonest fragment ion to be formed – either because there are several ways in which it could be produced during fragmentation of the parent ion, or because it is a particularly stable ion.
– What is base peak in mass spectrometry?
Base peak: The most intense (tallest) peak in a mass spectrum, due to the ion with the greatest relative abundance (relative intensity; height of peak along the spectrum’s y-axis). The electron impact ionization mass spectrum of methane, in which the base peak is M having m/z = 16.
– why is ionisation necessary in a mass spectrometer?
Because a mass spectrometer works by moving the particles it’s examining with electric and magnetic fields. If a particle is not ionised then it has zero charge and it’s mass to charge ratio is identical to all other uncharged particles – so you cannot determine its mass.
– what does M+ peak mean?
The M+ peak is usually the highest intensity peak in the cluster of peaks at highest m/z.
– what is mass spectrometry and how does it work?
A mass spectrometer produces charged particles (ions) from the chemical substances that are to be analyzed. The mass spectrometer then uses electric and magnetic fields to measure the mass (“weight”) of the charged particles.
– where is mass spectrometry used?
Specific applications of mass spectrometry include drug testing and discovery, food contamination detection, pesticide residue analysis, isotope ratio determination, protein identification, and carbon dating.
– what are the labels on the axes of a mass spectrum?
The charged particles are deflected by the magnetic field according to their mass and charge. The x-axis label is atomic weight and the y- axis label is signal intensity.
The Y axis is labeled relative intensity. This is the intensity relative to the tallest peak in the spectrum with the tallest peak set to 100%. The X axis is mass divided by charge, m/z.
– how do you calculate relative atomic mass using mass spectrum? how to calculate relative atomic mass from mass spectrum?
The average mass would therefore be, the total mass divided by the total number of atoms. i.e. 1330/123 = 10.8 which is the relative atomic mass (RAM) of Boron. The other method is to express the y-axis as the “Relative abundance %”. The mass spectrum of Zirconium is shown below.
– what is the formula of finding relative atomic mass? How to Find Relative Mass?

 

Isotope. Relative isotopic mass. Relative abundance (%) Cl Ar = (relative isotopic mass X1 % abundance) + relative isotopic mass X2 % abundance) 100. Ar (Cl) = ( X 75.8) + ( X 24.2) Ar (Cl) = Ar (Cl) = amu (atomic mass unit).

– What is relative molecular mass?

 

– is relative atomic mass and atomic mass the same?
“Atomic mass” is relative to the isotope carbon-12 weighing exactly 12 atomic mass units. Therefore “atomic mass” is precisely the same as “relative atomic mass.” First, atomic mass as stated on the periodic table is a average of the masses of an element’s naturally-occurring isotopes, weighted by their abundance.
– what its look like CO2 in mass spectrometry graph?
– what its look like fluorine in mass spectrometry graph?
– what its look like bromine in mass spectrometry graph?
– what its look like chlorine in mass spectrometry graph?
– what its look like iodine in mass spectrometry graph?
– what its look like propane in mass spectrometry graph?
– what its look like cyclopropane in mass spectrometry graph?
– what its look like boron trifluoride in mass spectrometry graph?
– what its look like NH3 in mass spectrometry graph?
– what its look like ClO2 in mass spectrometry graph?
– what its look like Pb in mass spectrometry graph?

1.3 The mole and the Avogadro constant

– what is a mole of particles’ concept?
– how much is a mole?
The mole and Avogadro’s number. One mole of a substance is equal to 6.022 × 10²³ units of that substance (such as atoms, molecules, or ions).
– what is the mass of 1 mole of hydrogen gas?
2 grams. One MOLE of hydrogen atoms contains the same number of atoms as the number of hydrogen molecules in one MOLE of hydrogen molecules, i.e., Avagadro’s number. However, one mole of hydrogen atoms has a mass of 1 gram while one MOLE of hydrogen molecules has a mass of 2 grams.
– what is the mass of 1 mole of hydrogen atom?
1 gram.
– what is the mass of 1 mole of hydrogen molecule?
2 grams.
– what is the mass of 1 mole of hydrogen?
1 gram.
– how many moles are in 10 grams of hydrogen?
5 mole.
– what is the mass of 1 mole of oxygen?
16 grams.
– what is the mass of 1 mole of oxygen gas?
32 grams.
– what is the mass of 1 mole of nitrogen gas?
28 grams.
– what is the mass of 1 mole of nitrogen?
14 grams.
– calculations with moles using Avogadro’s number?

1 Atoms, Molecules and Stoichiometry

1.1 Fundamental particles of an atom

Candidates should be able to:

(a) describe the properties of protons, neutrons and electrons in terms of their relative charges and relative masses;
(b) predict the behaviour of beams of protons, neutrons and electrons in both electric and magnetic fields;
(c) describe the distribution of mass and charges within an atom;
(d) determine the number of protons, neutrons and electrons present in both neutral and charged species of a given proton number and nucleon number;
(e) describe the contribution of protons and neutrons to atomic nuclei in terms of proton number and nucleon number;
(f) distinguish isotopes based on the number of neutrons present, and state examples of both stable and unstable isotopes.

1.2 Relative atomic, isotopic, molecular and formula masses

Candidates should be able to:

(a) define the terms relative atomic mass, Ar, relative isotopic mass, relative molecular mass, Mr, and relative formula mass based on 12C;
(b) interpret mass spectra in terms of relative abundance of isotopes and molecular fragments;
(c) calculate relative atomic mass of an element from the relative abundance of its isotopes or its mass spectrum.

1.3 The mole and the Avogadro constant

Candidates should be able to:

(a) define mole in terms of the Avogadro constant;
(b) calculate the number of moles of reactants, volumes of gases, volumes of solutions and concentrations of solutions;
(c) deduce stoichiometric relationships from the calculations above.

 

1 Atoms, Molecules and Stoichiometry

1.1 Fundamental particles of an atom

Candidates should be able to:

(a) describe the properties of protons, neutrons and electrons in terms of their relative charges and relative masses;

(b) predict the behaviour of beams of protons, neutrons and electrons in both electric and magnetic fields;

(c) describe the distribution of mass and charges within an atom;

(d) determine the number of protons, neutrons and electrons present in both neutral and charged species of a given proton number and nucleon number;

(e) describe the contribution of protons and neutrons to atomic nuclei in terms of proton number and nucleon number;

(f) distinguish isotopes based on the number of neutrons present, and state examples of both stable and unstable isotopes.

1.2 Relative atomic, isotopic, molecular and formula masses

Candidates should be able to:

(a) define the terms relative atomic mass, Ar, relative isotopic mass, relative molecular mass, Mr, and relative formula mass based on 12C;

(b) interpret mass spectra in terms of relative abundance of isotopes and molecular fragments;

(c) calculate relative atomic mass of an element from the relative abundance of its isotopes or its mass spectrum.

1.3 The mole and the Avogadro constant

Candidates should be able to:

(a) define mole in terms of the Avogadro constant;
(b) calculate the number of moles of reactants, volumes of gases, volumes of solutions and concentrations of solutions;
(c) deduce stoichiometric relationships from the calculations above.

 

 

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