Edexcel IGCSEChemistryGeneral Applications9 Marks

This question is about atoms and elements. (a) Explain why atoms are neutral.

(a)Explain why atoms are neutral.[2]
(b)Different atoms of the same element are called isotopes. (i) State one similarity and one difference between isotopes of the same element.[2]
(b)(ii)State why isotopes of the same element have the same chemical properties.[1]
(c)The diagram shows the arrangement of electrons in an atom of an element.[2]
(c)(ii)Explain why this element is unreactive.[2]

Mark scheme

Marking points from the official mark scheme. The mark or mark type is shown in brackets.

B1 for (a) number of protons equals number of electrons
B1 for (a) protons are positive and electrons are negative OR charges cancel out
B1 for (b)(i) Similarity: same number of protons / same atomic number / same electrons / same chemical properties
B1 for (b)(i) Difference: different number of neutrons / different mass number
B1 for (b)(ii) because they have the same number of electrons in the outer shell / same electronic configuration
B1 for (c)(i) Group 0 / Group 8 / Group 18 (noble gases)
B1 for (c)(i) period 3
M1 for (c)(ii) full outer shell of electrons / 8 electrons in outer shell
A1 for (c)(ii) does not need to lose, gain or share electrons / stable electronic configuration

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