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8th grade atoms, elements and the periodic table

8th grade (Year 9 in England) · 16 questions · Common Core: NGSS.MS-PS1-1, NGSS.HS-PS1-1, NGSS.HS-PS1-2, NGSS.HS-PS1-8 · England: KS3 Chemistry: Atoms, elements and compounds, KS4 Combined Science: Atomic structure and the periodic table, KS4 Combined Science: Chemical changes

Name

Date

Score/ 16

1
Question 1
Which number is the same for all isotopes of an element?
- A. the number of neutrons
- B. the relative mass
- C. the mass number
- D. the atomic number
Question 2
How many chlorine atoms (Cl) are in HCl?
Answer
3
Question 3
Atomic structure: which statement is true?
- A. Most of the mass of an atom is in the nucleus.
- B. Neutrons have a negative charge.
- C. The plum pudding model is today's accepted model of the atom.
- D. Protons and electrons have the same mass.
4
Question 4
Melting points: lithium 181 °C, sodium 98 °C, potassium 63 °C, rubidium 39 °C. Which is the best prediction for caesium?
- A. about 75 °C
- B. about 200 °C
- C. about 29 °C
- D. about 300 °C
Question 5
Complete the word equation: lithium + water → ? + hydrogen
Answer
6
Question 6
The noble gases: which statement is NOT true?
- A. Helium has a full outer shell with only two electrons.
- B. Noble gases are colourless at room temperature.
- C. Noble gases have eight electrons in every shell.
- D. Neon glows red-orange in electric signs.
7
Question 7
Why does reactivity decrease down group 7?
- A. The atoms lose electrons more easily
- B. The outer shell is further from the nucleus, so gaining an electron is harder
- C. The atoms have fewer outer electrons
- D. Halogens are metals
Question 8
How many H atoms are in one formula unit of C₂H₅OH?
Answer
Question 9
The diagram shows an atom of helium. How many electrons does it have?
coral + = proton · grey = neutron · purple − = electron
Answer
10
Question 10
The halogens: which statement is true?
- A. Iodine is more reactive than chlorine.
- B. Halogens have seven electrons in their outer shell.
- C. Halogens are found as single atoms.
- D. Boiling points of halogens decrease down the group.
Question 11
Chlorine has atomic number 17. How many neutrons are in the isotope chlorine-37?
Answer
12
Question 12
Which noble gas is used for shielding metal during welding?
- A. helium
- B. neon
- C. argon
13
Question 13
Models of the atom: which statement is NOT true?
- A. Scientific models change when new evidence is found.
- B. Bohr's model put electrons in shells at fixed distances.
- C. The electron was discovered before the nucleus.
- D. Most of the mass of an atom is in its electrons.
14
Question 14
Which particle has no charge?
- A. proton
- B. neutron
- C. electron
15
Question 15
Boiling points: helium −269 °C, neon −246 °C, argon −186 °C. What is the trend down the group?
- A. there is no pattern
- B. boiling point decreases
- C. boiling point increases
- D. boiling point stays the same
Question 16
How many atoms are there altogether in one molecule or formula unit of H₂O?
Answer

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Answer key: 8th grade atoms, elements and the periodic table

1. D. the atomic number
2. 1
3. A. Most of the mass of an atom is in the nucleus.
4. C. about 29 °C
5. lithium hydroxide
6. C. Noble gases have eight electrons in every shell.
7. B. The outer shell is further from the nucleus, so gaining an electron is harder
8. 6
9. 2
10. B. Halogens have seven electrons in their outer shell.
11. 20
12. C. argon
13. D. Most of the mass of an atom is in its electrons.
14. B. neutron
15. C. boiling point increases
16. 3