Atomic structure

Question 1

What are isotopes?

Answer 1

Isotopes are atoms of the same element with different numbers of neutrons, and hence different mass numbers.

Question 2

Why are chemical reactions identical in different isotopes of the same element?

Answer 2

Because they have the same electron arrangement.

Question 3

Are cations positive or negative?

Answer 3

They are positive.

Question 4

Are anions positive or negative?

Answer 4

They are negative.

Question 5

What did JJ Thomson do?

Answer 5

He discovered that atoms contain electrons in 1898. He proposed the ‘Plum Pudding’ model.

Question 6

What did Rutherford do?

Answer 6

His Alpha Particle Scattering Experiment showed that most of the atom is empty space with a tiny, dense, positive nucleus.

Question 7

What did Niels Bohr do?

Answer 7

Bohr improved Rutherford’s model by placing electrons in specific orbits, or energy levels. The modern atomic model was based on Bohr’s work.

Question 8

What was the Alpha Particle Scattering Experiment?

Answer 8

An experiment where alpha particles are fired at a very thin sheet of gold. It was expected for the particles to pass straight through the gold, but the results showed that while the majority of the particles did, some came back towards the alpha particle source. This led Rutherford to present his nuclear model of the atom.

Question 9

What is the nuclear model of the atom and who proposed it?

Answer 9

Rutherford did. It states the atom is mostly empty space with a tiny, dense, positive nucleus.

Question 10

What is mass spectrometry used for?

Answer 10

Mass spectrometry can be used to find
relative isotopic abundance and identify
elements.

It helps to calculate the relative atomic mass
of an element from the relative abundances
of its isotopes.

Question 11

What is an element?

Answer 11

An element is a substance that connot be broken down into simpler substances by chemical means.

Question 12

What are the three basic substructure of the nucleus and what are their charges?

Answer 12

Proton: 1
Neutron: 0
Electron: -1

Question 13

What does the atomic number refer to?

Answer 13

The number of protons in an atom.

Question 14

What does the atomic mass number refer to?

Answer 14

The total number of protons and neutrons in an atom.

Question 15

What is a mixture?

Answer 15

A mixture consists of two or more elements or compounds not
chemically combined together. The chemical properties of each
substance in the mixture are unchanged.

Question 16

Why do elementa in the same group have similar physical and chemical properties?

Answer 16

Because they have the same number of elevtronsa

Question 17

How are mixtures separated?

Answer 17

Mixtures can be separated by physical processes such as filtration,
crystallisation, simple distillation, fractional distillation and
chromatography.

Question 18

Describe the development of the current nuclear model of the atom.

Answer 18

Before the discovery of the electron, atoms were thought to be tiny
spheres that could not be divided.

The discovery of the electron led to the plum pudding model of the
atom. The plum pudding model suggested that the atom is a ball of
positive charge with negative electrons embedded in it.

The results from the alpha particle scattering experiment led to the
conclusion that the mass of an atom was concentrated at the centre
(nucleus) and that the nucleus was charged. This nuclear model
replaced the plum pudding model.

Niels Bohr adapted the nuclear model by suggesting that electrons
orbit the nucleus at specific distances. The theoretical calculations
of Bohr agreed with experimental observations.

Later experiments led to the idea that the positive charge of any
nucleus could be subdivided into a whole number of smaller
particles, each particle having the same amount of positive charge.
The name proton was given to these particles.

The experimental work of James Chadwick provided the evidence
to show the existence of neutrons within the nucleus. This was
about 20 years after the nucleus became an accepted scientific
idea.

Question 19

How small are atoms?

Answer 19

Atoms are very small, having a radius of about 0.1 nm (1 x 10-10 m).

Question 20

How small is the nucleus of an atom?

Answer 20

The radius of a nucleus is less than 1/10 000 of that of the atom
(about 1 x 10-14 m).

Question 21

How do you calculate relative atomic mass?

Answer 21

1. Multiply all the isotope masses by their respective percentage abundance.
2. Add them together.
3. Divide result by 100.

Question 22

How many electrons can the first shell take?

Answer 22

2 electrons

Question 23

How many electrons can the second and third shell take?

Answer 23

8 electrons

Question 24

How are elements in the periodic table ordered?

Answer 24

In order of atomic number.