GCSE Atomic Structure & Periodic Table 5 — Questions and Answers
Question 1: Mendeleev left gaps in his periodic table. Why was this considered a strength of his model?
- He admitted the table was incomplete
- The gaps successfully predicted properties of undiscovered elements (Correct answer)
- He arranged elements by atomic number
- The gaps matched the noble gases discovered later
Correct answer: The gaps successfully predicted properties of undiscovered elements
Mendeleev predicted elements like gallium and germanium, which were later discovered with properties matching his predictions.
Question 2: Which of the following best explains why atoms are electrically neutral?
- They contain equal numbers of protons and neutrons
- They contain equal numbers of protons and electrons (Correct answer)
- Neutrons cancel out the charge of electrons
- The nucleus has no overall charge
Correct answer: They contain equal numbers of protons and electrons
Protons carry +1 and electrons carry −1; equal numbers of each result in a net charge of zero.
Question 3: Element Q has the electron arrangement 2,8,6. In which group and period is it found?
- Group 6, Period 3 (Correct answer)
- Group 3, Period 6
- Group 6, Period 2
- Group 8, Period 3
Correct answer: Group 6, Period 3
Period = number of occupied shells (3), Group = outer electrons (6), so Group 6, Period 3 — sulfur.
Question 4: As you move down Group 1, the melting points of the alkali metals:
- Increase
- Decrease (Correct answer)
- Stay the same
- First decrease then increase
Correct answer: Decrease
Melting points decrease down Group 1 as atomic radius increases and metallic bonding becomes weaker.
Question 5: A fluorine atom has 9 protons. A fluoride ion (F⁻) has:
- 8 electrons
- 9 electrons
- 10 electrons (Correct answer)
- 9 protons and 8 electrons
Correct answer: 10 electrons
Fluorine gains 1 electron to form F⁻, so it has 9 protons and 10 electrons.
Question 6: In the alpha particle scattering experiment, what did the mostly undeflected particles suggest about the atom?
- The atom is mostly empty space (Correct answer)
- The nucleus is spread throughout the atom
- Electrons repel the alpha particles
- The atom has no nucleus
Correct answer: The atom is mostly empty space
The vast majority passing straight through indicated that the atom is mostly empty space with mass concentrated in a tiny nucleus.
Question 7: Which of the following pairs are isotopes of the same element?
- ¹²C and ¹⁴N
- ¹H and ²H (Correct answer)
- ¹⁶O and ³²S
- ²³Na and ²⁴Mg
Correct answer: ¹H and ²H
¹H (protium) and ²H (deuterium) are both hydrogen with 1 proton but different numbers of neutrons.
GCSE Atomic Structure & Periodic Table 5
Mendeleev left gaps in his periodic table.
Why was this considered a strength of his model?