4.1.1 A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

Question 1

What are substances made of, and what is the smallest part of an element that can exist?

Answer 1

All substances are made of atoms, which are the smallest parts of elements that can exist.

• Alternate question 1: What are the building blocks of substances, and what is the smallest unit of an element?
• Alternate question 2: What are all substances made from, and what is the tiniest part of an element?

Question 2

How are elements represented?

Answer 2

Each element is represented by a chemical symbol (e.g., O for oxygen, Na for sodium).

Question 3

How many elements are there, and where are they listed?

Answer 3

There are about 100 different elements, all listed in the periodic table.

Question 4

How are compounds formed?

Answer 4

Compounds are formed when elements chemically combine through reactions.

Question 5

What do chemical reactions produce, and what is often involved?

Answer 5

Chemical reactions produce new substances and often involve energy changes.

Question 6

What do compounds contain, and how are they represented?

Answer 6

Compounds contain two or more elements chemically combined in fixed proportions and are represented by formulae using the element symbols.

Question 7

How can compounds be separated into their elements?

Answer 7

Compounds can only be separated back into elements by chemical reactions.

Question 8

How can chemical reactions be written?

Answer 8

Chemical reactions can be written as word equations or using symbols and formulae.

Question 9

What is a mixture?

Answer 9

Mixtures consist of two or more elements or compounds not chemically combined, retaining their individual properties.

Question 10

How can mixtures be separated?

Answer 10

Mixtures can be separated by physical processes like filtration, crystallisation, simple distillation, fractional distillation, and chromatography. These methods do not involve chemical reactions or produce new substances.

Question 11

filteration technique

Question 12

fractional distilation technique

Question 13

simple distilation technique

Question 14

crystalisation technique

Question 15

chromotography technique

Question 16

What was the early idea of an atom?

Answer 16

Before electrons were discovered, atoms were thought to be indivisible spheres.

Question 17

What did the discovery of the electron lead to?

Answer 17

The discovery of the electron led to the plum pudding model (a positive sphere with embedded negative electrons).

Question 18

What did the alpha particle scattering experiment show?

Answer 18

The alpha particle scattering experiment showed that atoms have a small, dense, positively charged nucleus, leading to the nuclear model.

Question 19

How did Niels Bohr improve the atomic model?

Answer 19

Niels Bohr improved the model by proposing that electrons orbit the nucleus at specific distances.

Question 20

What are protons, and who identified them?

Answer 20

Protons are the particles carrying positive charge in the nucleus, later identified through experiments.

Question 21

Who provided evidence for neutrons, and when?

Answer 21

James Chadwick’s work provided evidence for neutrons in the nucleus, about 20 years after the nuclear model was developed.

Question 22

Why do atoms have no overall charge?

Answer 22

Atoms have no overall charge because the number of protons equals the number of electrons.

Question 23

What is the atomic number?

Answer 23

The atomic number is the number of protons in an atom, which is unique for each element.

Question 24

What are isotopes?

Answer 24

Atoms of the same element can have different numbers of neutrons, forming isotopes.

Question 25

What is the mass number?

Answer 25

The mass number is the total number of protons and neutrons in an atom.

Question 26

How small are atoms?

Answer 26

Atoms are extremely small, with a radius of about 0.1 nm (1 x 10⁻¹⁰ m).

Question 27

How small is the nucleus compared to the atom?

Answer 27

The nucleus is even smaller, about 1 x 10⁻¹⁴ m, and contains almost all the atom’s mass.

Question 28

What are the relative masses of subatomic particles?

Answer 28

Proton: 1

Neutron: 1

Electron: ~0

Question 29

What are the relative charges of subatomic particles?

Answer 29

Proton: +1

Neutron: 0

Electron: -1

Question 30

How can you calculate the number of protons, neutrons, and electrons in an atom or ion?

Question 31

What does the relative atomic mass (Ar) of an element account for?

Answer 31

The relative atomic mass (Ar) of an element accounts for the abundance of its isotopes.

Question 32

How can you calculate the relative atomic mass?

Question 33

Where do electrons occupy in an atom?

Answer 33

Electrons occupy the lowest available energy levels (innermost shells).

Question 34

How can the electronic structure of an atom be shown?

Answer 34

The electronic structure of an atom can be shown by numbers or diagrams (e.g., sodium: 2,8,1).

Question 35

What are energy levels?

Question 36

What are shells?