, PLEASE USE THIS DOCUMENT AS A GUIDE ONLY
QUESTION 1
1. Answer the following questions:
1.1. Define the term “particle” as used in physical science.
A particle is a small localised object which can be described by several physical or chemical
properties (NST2601, Study Unit 2. p. 15).
1.2. Identify the subatomic particle that was discovered by J.J. Thomson.
The subatomic particle discovered by J.J. Thomson is the electron (NST2601, Study Unit 2. p. 19).
1.3. Recall the scientist who proposed the billiard ball model of the atom.
The scientist who proposed the billiard ball model of the atom is John Dalton (NST2601, Study Unit
2. p. 17).
1.4. State the electrical charge of a neutron.
The electrical charge of a neutron is neutral (no charge) (NST2601, Study Unit 2. p. 29).
1.5. Determine the maximum number of electrons that can occupy the second energy
shell.
The maximum number of electrons that can occupy the second energy shell is 8 (using the formula
2n2, where n=2:2 × 22 = 8 (NST2601, Study Unit 2. p. 37).
1.6. Recognize the atomic model that proposes fixed energy level orbits for electrons.
The atomic model that proposes fixed energy level orbits for electrons is Bohr's model (planetary
model) (NST2601, Study Unit 2. p. 25).
1.7. Write the symbol that represents a proton.
The symbol that represents a proton is P+ (NST2601, Study Unit 2. p. 29).
1.8. Indicate the atomic number of chlorine on the periodic table.
The atomic number of chlorine on the periodic table is 17 (NST2601, Study Unit 2. p. 30).
1.9. Recall the scientific term for atoms of the same element that have different numbers of
neutrons.
The scientific term for atoms of the same element that have different numbers of neutrons is isotopes
(NST2601, Study Unit 2. p. 31).
, 1.10. Identify the part of an atom that is described as the positively charged center.
The part of an atom described as the positively charged center is the nucleus (NST2601, Study Unit
2. p. 28).
QUESTION 2
2. Provide answers to the following questions.
2.1. Explain why cathode rays bend toward a positively charged plate.
Cathode rays bend toward a positively charged plate because they are composed of negatively
charged particles (electrons). Opposites attract, so the negative cathode ray particles are attracted to
the positive plate and deflected away from the negatively charged plate (NST2601, Study Unit 2. p.
18).
2.2. Describe how Rutherford’s gold foil experiment led to the rejection of the plum pudding
model.
In Rutherford’s gold foil experiment, most alpha particles passed straight through the gold foil, but a
small number were deflected and even bounced back. According to the plum pudding model (where
positive charge was spread evenly throughout the atom), Rutherford expected all alpha particles to
bounce back. The fact that only a few were deflected and some bounced back indicated that the
atom’s positive charge is concentrated in a tiny, dense nucleus, not distributed uniformly. This
contradicted the plum pudding model and led to its rejection in favour of the nuclear model
(NST2601, Study Unit 2. pp. 22-23).
2.3. Define the concept of electron configuration in an atom.
Electron configuration is the arrangement and distribution of electrons in the space around an atom’s
nucleus. It helps to keep track of where the electrons are in a given atom (NST2601, Study Unit 2. p.
36).
2.4. Illustrate the relationship between the atomic number and the number of electrons in a
neutral atom.
In a neutral atom, the number of electrons is equal to the atomic number (the number of protons). For
example, magnesium has an atomic number of 12, so a neutral magnesium atom has 12 electrons;
chlorine has an atomic number of 17, so a neutral chlorine atom has 17 electrons (NST2601, Study
Unit 2. p. 30).
2.5. Explain why isotopes of the same element have similar chemical properties.
Isotopes of the same element have the same number of protons and therefore the same number of
electrons (including the same number of valence electrons). Since chemical properties are
determined by the arrangement and behaviour of electrons (particularly valence electrons), isotopes
exhibit nearly identical chemical behaviour (NST2601, Study Unit 2. pp. 31-32).
QUESTION 1
1. Answer the following questions:
1.1. Define the term “particle” as used in physical science.
A particle is a small localised object which can be described by several physical or chemical
properties (NST2601, Study Unit 2. p. 15).
1.2. Identify the subatomic particle that was discovered by J.J. Thomson.
The subatomic particle discovered by J.J. Thomson is the electron (NST2601, Study Unit 2. p. 19).
1.3. Recall the scientist who proposed the billiard ball model of the atom.
The scientist who proposed the billiard ball model of the atom is John Dalton (NST2601, Study Unit
2. p. 17).
1.4. State the electrical charge of a neutron.
The electrical charge of a neutron is neutral (no charge) (NST2601, Study Unit 2. p. 29).
1.5. Determine the maximum number of electrons that can occupy the second energy
shell.
The maximum number of electrons that can occupy the second energy shell is 8 (using the formula
2n2, where n=2:2 × 22 = 8 (NST2601, Study Unit 2. p. 37).
1.6. Recognize the atomic model that proposes fixed energy level orbits for electrons.
The atomic model that proposes fixed energy level orbits for electrons is Bohr's model (planetary
model) (NST2601, Study Unit 2. p. 25).
1.7. Write the symbol that represents a proton.
The symbol that represents a proton is P+ (NST2601, Study Unit 2. p. 29).
1.8. Indicate the atomic number of chlorine on the periodic table.
The atomic number of chlorine on the periodic table is 17 (NST2601, Study Unit 2. p. 30).
1.9. Recall the scientific term for atoms of the same element that have different numbers of
neutrons.
The scientific term for atoms of the same element that have different numbers of neutrons is isotopes
(NST2601, Study Unit 2. p. 31).
, 1.10. Identify the part of an atom that is described as the positively charged center.
The part of an atom described as the positively charged center is the nucleus (NST2601, Study Unit
2. p. 28).
QUESTION 2
2. Provide answers to the following questions.
2.1. Explain why cathode rays bend toward a positively charged plate.
Cathode rays bend toward a positively charged plate because they are composed of negatively
charged particles (electrons). Opposites attract, so the negative cathode ray particles are attracted to
the positive plate and deflected away from the negatively charged plate (NST2601, Study Unit 2. p.
18).
2.2. Describe how Rutherford’s gold foil experiment led to the rejection of the plum pudding
model.
In Rutherford’s gold foil experiment, most alpha particles passed straight through the gold foil, but a
small number were deflected and even bounced back. According to the plum pudding model (where
positive charge was spread evenly throughout the atom), Rutherford expected all alpha particles to
bounce back. The fact that only a few were deflected and some bounced back indicated that the
atom’s positive charge is concentrated in a tiny, dense nucleus, not distributed uniformly. This
contradicted the plum pudding model and led to its rejection in favour of the nuclear model
(NST2601, Study Unit 2. pp. 22-23).
2.3. Define the concept of electron configuration in an atom.
Electron configuration is the arrangement and distribution of electrons in the space around an atom’s
nucleus. It helps to keep track of where the electrons are in a given atom (NST2601, Study Unit 2. p.
36).
2.4. Illustrate the relationship between the atomic number and the number of electrons in a
neutral atom.
In a neutral atom, the number of electrons is equal to the atomic number (the number of protons). For
example, magnesium has an atomic number of 12, so a neutral magnesium atom has 12 electrons;
chlorine has an atomic number of 17, so a neutral chlorine atom has 17 electrons (NST2601, Study
Unit 2. p. 30).
2.5. Explain why isotopes of the same element have similar chemical properties.
Isotopes of the same element have the same number of protons and therefore the same number of
electrons (including the same number of valence electrons). Since chemical properties are
determined by the arrangement and behaviour of electrons (particularly valence electrons), isotopes
exhibit nearly identical chemical behaviour (NST2601, Study Unit 2. pp. 31-32).
