unit 1: t3- atoms

Question 1

Describe how the Dalton model of an atom has changed over time because of the discovery of subatomic particles

Answer 1

• the Dalton model has changed over time because of the discovery of subatomic particles.
• atoms can be broken down into three smaller particles: protons, neutrons and electrons
• atoms of an element have identical numbers of protons and electrons, but can have different numbers of neutrons
• atoms of different elements have different numbers of protons and electrons

Question 2

Describe the structure of an atom as a nucleus containing protons and neutrons, surrounded by electrons in shells

Answer 2

An atom has a central nucleus (made up of protons and neutrons) surrounded by electrons arranged in areas called shells.

Question 3

the relative charge and mass of a proton

Answer 3

• relative charge: +1

- relative mass: 1

Question 4

the relative charge and mass of a neutron

Answer 4

• relative charge: 0

- relative mass: 1

Question 5

the relative charge and mass of an electron

Answer 5

• relative charge: -1

- relative mass: 1/1835

Question 6

Explain why atoms contain equal numbers of protons and electrons

Answer 6

• it has an equal number of negative electric charges (the electrons) and positive electric charges (the protons)
• the total electric charge of the atom is therefore zero and the atom is said to be neutral

Question 7

Recall that most of the mass of an atom is concentrated in the nucleus

Answer 7

Since the nucleus contains protons and neutrons, most of the mass of an atom is concentrated in its nucleus