C1 -Atomic Structure and the periodic table

Explain why an atom has no overall electrical charge.(2 marks)

• 1 mark: Equal number of protons and electrons.

• 1 mark: Positive and negative charges cancel out.

Explain why chlorine-35 and chlorine-37 have the same chemical properties.(2 marks)

• 1 mark: They have the same number of electrons / electronic structure.

• 1 mark: Therefore they have the same chemical properties

Describe Dalton's model of the atom?(1 mark)

Atoms are solid spheres that cannot be divided

Explain what the alpha scattering experiment showed about the structure of the atom.(2 marks)

• 1 mark: The atom has a small, dense nucleus containing most of the mass.

• 1 mark: The nucleus is positively charged and most of the atom is empty space.

Explain why magnesium forms a 2+ ion.(2 marks)

• 1 mark: Magnesium loses two electrons.

• 1 mark: This gives it a full outer shell.

Explain why Group 1 elements become more reactive as you go down the group.(3 marks)

• 1 mark: More electron shells.

• 1 mark: Greater distance between the nucleus and outer electron.

• 1 mark: Outer electron is easier to lose.

Explain why Mg²⁺ has a 2+ charge.(1 mark)

Losing two negatively charged electrons leaves two more protons than electrons, giving an overall 2+ charge.

Explain why elements in the same group have similar chemical properties.(2 marks)

• 1 mark: They have the same number of outer-shell electrons.

• 1 mark: Therefore they have similar chemical properties

Explain why Group 1 becomes more reactive down the group.(3 marks)

• 1 mark: More electron shells.

• 1 mark: Greater distance between the nucleus and outer electron.

• 1 mark: Outer electron is easier to lose.

Explain why Group 7 becomes less reactive down the group(2 marks)

• 1 mark: More electron shells → greater distance so weaker attraction for an incoming electron.

• 1 mark: Therefore it is harder to gain an electron.