Unit 3 - Atomic Structure

Question 1

What are the 4 parts to John Dalton’s theory about the atom

Answer 1

All matter is made of tiny particles called atoms
Atoms are tiny hard spheres that can’t be broken down into smaller parts
Atoms can’t be created or destroyed
Atoms in an element are identical but each element is different

Question 2

Who disproved John Dalton’s particle theory?

Answer 2

JJ Thomson

Question 3

What experiment discovered subatomic particles?

Answer 3

When a high voltage was applied to a glass tube with most air removed, a glowing ray was seen. Thomson discovered these particles had the mass of 1800 times lighter than the lightest atom. The rays contained subatomic particles called electrons.

Question 4

What subatomic particles make up an atom

Answer 4

Protons, neutrons, electrons

Question 5

What does the relative mass and relative charge do?

Answer 5

It helps is to describe the subatomic particles compared to a proton (charge and mass of 1)

Question 6

Why do atoms have no charge

Answer 6

They have an equal number of protons and electrons, they cancel out

Question 7

What is the diameter of the nucleus of an atom to the whole atom?

Answer 7

100,000 times smaller

Question 8

What experiment did Ernest Rutherford carry out?

Answer 8

Shot alpha particles at thin gold.
Most passed through but some reflected back.
Shows empty space with dense nucleus containing most of the mass.

Question 9

How were the elements in the periodic table originally placed?

Answer 9

Order of masses

Question 10

How are the elements in the periodic table ordered.

Answer 10

In order of the amount of +ve charge in the nucleus

Question 11

What is the atomic number

Answer 11

The number of protons in the element

Question 12

Why does their nucleus of an atom contain nearly all its mass

Answer 12

Electrons have so little mass

Question 13

What is the mass number

Answer 13

The number of protons and neutrons in an atom

Question 14

What is the symbol for the mass number

Answer 14

A

Question 15

What is the symbol for the atomic number

Answer 15

Z

Question 16

What are isotopes.

Answer 16

The same element that has a different mass due to the number of neutrons

Question 17

What did the understanding of neutrons lead to

Answer 17

The discovery of nuclear energy

Question 18

What is the isotope which atom masses are always compared to

Answer 18

Carbon-12

Question 19

Why is the relative mass of helium-4 one third of that f carbon-12?

Answer 19

Everything is compared to carbon-12 so 3 atoms of helium-4 have the same mass as carbon-12

Question 20

What so the relative atomic mass of an Atom?

Answer 20

The mean mass of an atom or an element compared with carbon-12

Question 21

How is the relative atomic mass of an atom calculated? ( 75% of chlorine-75 and 25% of chlorine-37 )

Answer 21

E.g 75% of chlorine-35 and 25% of chlorine-37
Assume there are 100 atoms as it will = 100%
(75x35)+(25x37)/100
Ar = 35.5

Question 22

What is the abbreviation and symbol for the relative atomic mass?

Answer 22

RAM and Ar

Question 23

What is the method for working out the RAM

Answer 23

RAM = total mass of the atoms/ the number of atoms