Complete the table of relative properties of subatomic particles . Particle Relative charge Relative mass Proton .......... .......... Neutron .......... .......... Electron .......... ..........

Particle Relative charge Relative mass Proton +1 1 Neutron 0 1 Electron -1 1/1836 (negligible)

Define atomic number .

An atomic number ( Z ) is the number of protons in the nucleus of an atom. It is unique to each element and determines the element's identity.

Define atomic radius .

An atomic radius is a measure of the size of an atom. It is defined as half the distance between the nuclei of two covalently bonded atoms of the same element .

Why does a beam of electrons deflect more than a beam of protons in the same electric field?

Electrons deflect more because their mass (~1/1836 that of a proton) is far smaller. The same electrostatic force produces a much greater acceleration on the lighter electron, causing stronger deflection.

Number of neutrons = .......... − .......... .

Number of neutrons = mass number ( A ) − atomic number ( Z ) .

Why does atomic radius decrease across a period?

Across a period, nuclear charge increases as more protons are added, but electrons are added to the same principal quantum shell . The stronger nuclear pull draws electrons closer to the nucleus, decreasing the atomic radius .

True or False? In a neutral atom, the number of electrons equals the number of protons .

True. A neutral atom carries no overall charge, so the negatively charged electrons must exactly balance the positively charged protons in the nucleus .

A mass number ( A ) is the total number of protons and neutrons in the nucleus of an atom. It is also called the nucleon number .

True or False? Atomic radius increases across a period as more electrons are added to the outer shell .

False. Atomic radius decreases across a period. Although electrons are added to the same shell, the increasing nuclear charge pulls electrons closer to the nucleus, reducing the radius.

A nucleon is a particle found in the nucleus of an atom. Both protons and neutrons are nucleons.

A Cl - ion has atomic number 17 and mass number 35. How many protons , neutrons , and electrons does it have?

A Cl - ion has: Protons: 17 (= atomic number) Neutrons: 18 (= 35 − 17) Electrons: 18 (= 17 + 1, because Cl - has gained 1 electron)

Why does atomic radius increase down a group?

Moving down a group, each element has an additional principal quantum shell . Electrons in inner shells shield outer electrons from the nuclear charge, weakening the attraction and increasing the atomic radius .

What happens to a beam of neutrons passing through an electric field?

A beam of neutrons passes straight through without deflection . Neutrons carry no charge and are therefore unaffected by the electric field.

True or False? A Mg 2+ ion (atomic number 12) has 12 electrons .

False. A Mg 2+ ion has 10 electrons . Magnesium has atomic number 12, but the 2+ charge means it has lost 2 electrons , leaving 10.

Ionic radius .......... with increasing negative charge, and .......... with increasing positive charge.

Ionic radius increases with increasing negative charge, and decreases with increasing positive charge.

In an atom, the .......... contains protons and neutrons , while .......... orbit in shells at increasing distances from the nucleus.

In an atom, the nucleus contains protons and neutrons , while electrons orbit in shells at increasing distances from the nucleus.

Why does a positive ion have a positive charge?

A positive ion forms when an atom loses one or more electrons. This leaves more protons than electrons, so the particle has more positive charge than negative charge, giving it an overall positive charge .

Why is a negative ion larger than its parent atom?

A negative ion forms by gaining extra electrons while the nuclear charge stays the same. The greater number of electrons experience a weaker pull from the nucleus, so the ionic radius increases.

Why does the nucleus carry an overall positive charge ?

The nucleus contains protons (relative charge +1) and neutrons (no charge). The positive charges of the protons are unopposed within the nucleus, giving it an overall positive charge .

True or False? All ions of the same element have the same number of protons .

True. The number of protons (the atomic number ) is fixed for a given element and does not change when electrons are gained or lost. Only the number of electrons changes when ions form.

True or False? A Ca 2+ ion is smaller than a neutral Ca atom.

True. A Ca 2+ ion has lost 2 electrons while the nuclear charge stays the same. Fewer electrons experience a stronger pull, reducing the ionic radius compared to the neutral calcium atom.

True or False? The mass of an atom is concentrated in the nucleus .

True. Protons and neutrons each have a relative mass of 1, while the electron mass (~1/1836) is negligible. Almost all the mass of an atom is therefore found in the nucleus .

An unknown atom X has mass number 63 and 34 neutrons. How many protons does it have, and what element is it?

Atom X has 29 protons (= 63 − 34). An element with atomic number 29 is copper (Cu).

Why does atomic radius increase sharply between a noble gas and the alkali metal that starts the next period?

The alkali metal at the start of the next period has one extra principal quantum shell compared to the noble gas. This additional shell greatly increases shielding and distance from the nucleus, causing a sharp rise in atomic radius .

An atom is the smallest particle of an element that can take part in a chemical reaction . It consists of a central nucleus containing protons and neutrons , surrounded by electrons in shells .

Positive ions form when atoms .......... electrons, giving them .......... electrons than protons. Negative ions form when atoms .......... electrons.

Positive ions form when atoms lose electrons, giving them fewer electrons than protons. Negative ions form when atoms gain electrons.

Atomic radius generally .......... across a period and .......... down a group.

Atomic radius generally decreases across a period and increases down a group.

In which direction is a beam of protons deflected in an electric field?

A beam of protons is deflected slightly toward the negative plate . Protons carry a positive charge and are attracted to the negative plate, but deflect less than electrons due to their much greater mass .

A LevelChemistryCambridge (CIE)Flashcards1. Atomic StructureParticles in the Atom & Atomic Radius

Particles in the Atom & Atomic Radius (Cambridge (CIE) A Level Chemistry): Flashcards

Exam code: 9701

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FrontAtomic Structure & Subatomic Particles
Complete the table of relative properties of subatomic particles.
Particle
Relative charge
Relative mass
Proton
..........
..........
Neutron
..........
..........
Electron
..........
..........

Particle	Relative charge	Relative mass
Proton	..........	..........
Neutron	..........	..........
Electron	..........	..........

Particle	Relative charge	Relative mass
Proton	+1	1
Neutron	0	1
Electron	-1	1/1836 (negligible)

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Complete the table of relative properties of subatomic particles.
Particle
Relative charge
Relative mass
Proton
..........
..........
Neutron
..........
..........
Electron
..........
..........
Particle
Relative charge
Relative mass
Proton
+1
1
Neutron
0
1
Electron
-1
1/1836 (negligible)
Define atomic number.
An atomic number (Z) is the number of protons in the nucleus of an atom. It is unique to each element and determines the element's identity.
Define atomic radius.
An atomic radius is a measure of the size of an atom. It is defined as half the distance between the nuclei of two covalently bonded atoms of the same element.
Why does a beam of electrons deflect more than a beam of protons in the same electric field?
Electrons deflect more because their mass (~1/1836 that of a proton) is far smaller. The same electrostatic force produces a much greater acceleration on the lighter electron, causing stronger deflection.
Number of neutrons = .......... − ...........
Number of neutrons = mass number (A) − atomic number (Z).
Why does atomic radius decrease across a period?
Across a period, nuclear charge increases as more protons are added, but electrons are added to the same principal quantum shell. The stronger nuclear pull draws electrons closer to the nucleus, decreasing the atomic radius.
True or False?
In a neutral atom, the number of electrons equals the number of protons.
True.
A neutral atom carries no overall charge, so the negatively charged electrons must exactly balance the positively charged protons in the nucleus.
Define mass number.
A mass number (A) is the total number of protons and neutrons in the nucleus of an atom. It is also called the nucleon number.
True or False?
Atomic radius increases across a period as more electrons are added to the outer shell.
False.
Atomic radius decreases across a period. Although electrons are added to the same shell, the increasing nuclear charge pulls electrons closer to the nucleus, reducing the radius.
Define nucleon.
A nucleon is a particle found in the nucleus of an atom. Both protons and neutrons are nucleons.
A Cl^- ion has atomic number 17 and mass number 35. How many protons, neutrons, and electrons does it have?
A Cl^- ion has:
1. Protons: 17 (= atomic number)
2. Neutrons: 18 (= 35 − 17)
3. Electrons: 18 (= 17 + 1, because Cl^- has gained 1 electron)
Why does atomic radius increase down a group?
Moving down a group, each element has an additional principal quantum shell. Electrons in inner shells shield outer electrons from the nuclear charge, weakening the attraction and increasing the atomic radius.
What happens to a beam of neutrons passing through an electric field?
A beam of neutrons passes straight through without deflection. Neutrons carry no charge and are therefore unaffected by the electric field.
True or False?
A Mg²⁺ ion (atomic number 12) has 12 electrons.
False.
A Mg²⁺ ion has 10 electrons. Magnesium has atomic number 12, but the 2+ charge means it has lost 2 electrons, leaving 10.
Ionic radius .......... with increasing negative charge, and .......... with increasing positive charge.
Ionic radius increases with increasing negative charge, and decreases with increasing positive charge.
In an atom, the .......... contains protons and neutrons, while .......... orbit in shells at increasing distances from the nucleus.
In an atom, the nucleus contains protons and neutrons, while electrons orbit in shells at increasing distances from the nucleus.
Why does a positive ion have a positive charge?
A positive ion forms when an atom loses one or more electrons. This leaves more protons than electrons, so the particle has more positive charge than negative charge, giving it an overall positive charge.
Why is a negative ion larger than its parent atom?
A negative ion forms by gaining extra electrons while the nuclear charge stays the same. The greater number of electrons experience a weaker pull from the nucleus, so the ionic radius increases.
Why does the nucleus carry an overall positive charge?
The nucleus contains protons (relative charge +1) and neutrons (no charge). The positive charges of the protons are unopposed within the nucleus, giving it an overall positive charge.
True or False?
All ions of the same element have the same number of protons.
True.
The number of protons (the atomic number) is fixed for a given element and does not change when electrons are gained or lost. Only the number of electrons changes when ions form.
True or False?
A Ca²⁺ ion is smaller than a neutral Ca atom.
True.
A Ca²⁺ ion has lost 2 electrons while the nuclear charge stays the same. Fewer electrons experience a stronger pull, reducing the ionic radius compared to the neutral calcium atom.
True or False?
The mass of an atom is concentrated in the nucleus.
True.
Protons and neutrons each have a relative mass of 1, while the electron mass (~1/1836) is negligible. Almost all the mass of an atom is therefore found in the nucleus.
An unknown atom X has mass number 63 and 34 neutrons. How many protons does it have, and what element is it?
Atom X has 29 protons (= 63 − 34). An element with atomic number 29 is copper (Cu).
Why does atomic radius increase sharply between a noble gas and the alkali metal that starts the next period?
The alkali metal at the start of the next period has one extra principal quantum shell compared to the noble gas. This additional shell greatly increases shielding and distance from the nucleus, causing a sharp rise in atomic radius.
Define atom.
An atom is the smallest particle of an element that can take part in a chemical reaction. It consists of a central nucleus containing protons and neutrons, surrounded by electrons in shells.
Positive ions form when atoms .......... electrons, giving them .......... electrons than protons. Negative ions form when atoms .......... electrons.
Positive ions form when atoms lose electrons, giving them fewer electrons than protons. Negative ions form when atoms gain electrons.
Atomic radius generally .......... across a period and .......... down a group.
Atomic radius generally decreases across a period and increases down a group.
In which direction is a beam of protons deflected in an electric field?
A beam of protons is deflected slightly toward the negative plate. Protons carry a positive charge and are attracted to the negative plate, but deflect less than electrons due to their much greater mass.

Particle	Relative charge	Relative mass
Proton	..........	..........
Neutron	..........	..........
Electron	..........	..........

Particle	Relative charge	Relative mass
Proton	+1	1
Neutron	0	1
Electron	-1	1/1836 (negligible)

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