Chapter 2

Question 1

What was Dalton’s contribution to atomic theory?

Answer 1

Said that each element is made up of very small, indivisible particles called atoms.

Question 2

What was Thomson’s contribution to atomic theory?

Answer 2

Proposed the plum pudding model of the atom which described the atom as consisting of negatively charged particles embedded in the positive matter.

Question 3

What was Rutherford’s contribution to atomic theory?

Answer 3

That most of the atom is empty space with most of the mass located in a tiny central region called the nucleus. This region was positively charged with electrons moving around it in circular orbits.

Question 4

What was Chadwick’s contribution to atomic theory?

Answer 4

Discovered the neutron in the nucleus of the atom.

Question 5

What is a neutron?

Answer 5

A neutral particle found in the nucleus of an atom. It has the same mass as the proton, but is without charge.

Question 6

What is a proton?

Answer 6

A positively charged particle found in the nucleus of an atom.

Question 7

What is the atomic number?

Answer 7

The number of protons in the nucleus.

Question 8

What is the mass number?

Answer 8

The sum of the number of protons and neutrons.

Question 9

What are isotopes?

Answer 9

Atoms with the same number of protons but different number of neutrons.

Question 10

What are ions?

Answer 10

Ions are charged atoms, formed when electrons are gained or lost.

Question 11

What are cations?

Answer 11

Positively charged atoms formed when electrons are lost.

Question 12

What are anions?

Answer 12

Negatively charged atoms formed when electrons are gained.

Question 13

What did Bohr contribute to atomic theory?

Answer 13

Proposed that electrons orbit the nucleus in shells of specific energy.

Question 14

Describe shell number 1

Answer 14

It is the closest to the nucleus and can contain a maximum of 2 electrons.

Question 15

Describe shell number 2

Answer 15

It is the second closest to the nucleus and can contain a maximum of 8 electrons.

Question 16

Describe shell number 3

Answer 16

it is the third closest to the nucleus and can contain a maximum of 18 electrons.

Question 17

What is the rule for determining the maximum number of electrons in a shell?

Answer 17

2

2n - no outer shell may contain more than 8 electrons until there are at least 2 electrons in the following shell.

Question 18

What was Schrodinger’s contribution to atomic theory?

Answer 18

Proposed that electrons behave like a cloud of negative charge. Electrons are thought to move in regions of space surrounding the nucleus called orbitals.

Question 19

What is the maximum number of electrons in an orbital?

Answer 19

2

Question 20

Orbitals of similar energy are grouped together in sub-shells labelled?

Answer 20

s, p, d, f

Question 21

What are sub-shells?

Answer 21

Energy levels within the major energy shells.

Question 22

What is the order of filling sub-shells? And what is this called?

Answer 22

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 5p…

This is called the ground state electronic configuration.

Question 23

When is an atom in an excited state?

Answer 23

If electrons are present in a higher energy sub-shell when one of lower energy is not filled.