HMH Science Dimensions Chemistry Unit 2 Lesson 1

1.

Multiple Choice

30 sec

1 pt

Chlorine has a total of 17 electrons and 7 valence electrons. Why are these two numbers different?

Valence electrons are the electrons in the innermost orbital.

Valence electrons are the electrons in the outermost energy shell.

Some electrons are located in the nucleus of the atom.

Some electrons are located outside the atom.

2.

Multiple Choice

30 sec

1 pt

Why does the mass number for an element differ from the average atomic mass for that element?

The mass number only accounts for the number of protons, while the average atomic mass only accounts for the average number of neutrons.

The mass number accounts for the number of protons and neutrons, while the average atomic mass only accounts for the average number of protons.

The mass number accounts for the mass of each isotope. The average atomic mass is a weighted average of the number of neutrons.

The mass number only accounts for the mass of protons and neutrons, while the average atomic mass is a weighted average of the masses of the isotopes.

3.

Multiple Choice

30 sec

1 pt

Strontium has an atomic number of 38 and an atomic mass number of 88. Therefore it has how many PROTONS?

38

50

88

4.

Multiple Choice

30 sec

1 pt

Strontium has an atomic number of 38 and an atomic mass number of 88. Therefore it has how many NEUTRONS?

38

50

88

5.

Multiple Choice

30 sec

1 pt

Strontium has an atomic number of 38 and an atomic mass number of 88. Therefore it has how many ELECTRONS?

38

50

88

6.

Multiple Choice

30 sec

1 pt

Electron-dot notation shows only the electrons in which part of the atom?

innermost

outermost

7.

Multiple Choice

30 sec

1 pt

The electrons in the outermost energy shell of an atom are called _______.

valence electrons

orbital electrons

8.

Multiple Choice

30 sec

1 pt

The valence electrons __________ involved in chemical reactions.

are

are not

9.

Multiple Choice

30 sec

1 pt

Elements with a full outer energy shell are typically _________.

very reactive

unreactive

10.

Multiple Select

30 sec

1 pt

A scientist picks up a sample of an element. She thinks it might be a metal. Which of the following properties would support her conclusion? Select all correct answers.

element is shiny

element is dull

element partially conducts electricity

element is a good conductor of electricity

element is very brittle

11.

Multiple Select

30 sec

1 pt

Which of these claims are supported by the results of a flame test? Select all correct answers.

different metallic elements give off different colors when they are burned in a flame

electrons absorb energy when they move from one atom to another

protons absorb light when exposed to electricity

neutrons give off energy in the form of light when they absorb energy from a source such as a flame

electrons emit energy when they move from a higher energy level to a lower energy level

12.

Multiple Choice

5 mins

1 pt

Which is the electron configuration for an oxygen atom?

1s²2s²2p⁶3s²3p⁶4s²

1s²2s²2p⁴

1s²2s²2p⁶

1s²2s²2p⁶3s²3p⁶

13.

Multiple Choice

5 mins

1 pt

What atom matches this electron configuration?
1s²2s²2p⁶3s²

Neon

Magnesium

Aluminum

Potassium

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