Atomic Structure

Question 1

If the following diagram represents a helium nucleus, what subatomic particle is the arrow pointing to?

Answer 1

A proton.

Question 2

If the following diagram represents a helium nucleus, what subatomic particle is the arrow pointing to?

Answer 2

A neutron.

Question 3

The following diagram represents a helium nucleus. What is its atomic number?

Answer 3

The atomic number of a helium atom is 2, because it has two protons.

Question 4

The following diagram is a helium nucleus. Is the atomic mass 2 amu’s, 4 amu’s or 4.003 amus?

Answer 4

The mass of this helium nucleus is 4 amu’s because it has a total of 4 protons and neutrons, and each proton has a mass of 1 amu and each neutron has a mass of one amu.

Question 5

What does AMU stand for?

Answer 5

AMU stands for atomic mass unit.

Question 6

Which two subatomic particles are located in the nucleus of an atom?

Answer 6

Protons

and

neutons.

Question 7

Where are electrons located in an atom?

Answer 7

Electrons are located in orbitals surrounding the nucleus.

Question 8

The majority of an atom’s volume is composed of:

protons,

neutrons,

electrons,

or empty space?

Answer 8

Empty space.

Question 9

The density of an atom’s nucleus is:

very high,

high,

moderate,

or low?

Answer 9

Very high.

The nucleus of an atom is extraordinarily dense due to the very small volume that it occupies.

Question 10

The subatomic particle which bears a negative charge is

Answer 10

an electron.

Question 11

The subatomic particle which carries a positive charge is

Answer 11

a proton.

Question 12

Which subatomic particle has no charge?

Answer 12

A neutron.

Question 13

An atom has an atomic number of 3 and an atomic mass of 7. How many protons, neutrons, and electrons does this atom have?

Answer 13

3 protons

4 neutrons

and

3 electrons.

Question 14

The periods on the periodic table correspond to

Answer 14

electron shells or energy levels. That is, the first period has electrons in the first energy level; the second period has electrons in the second energy level, and so on.

Question 15

On the periodic table, atoms with the same number of valence electrons are located

Answer 15

in the same group.

Question 16

A subatomic particle has a mass of 1amu and a charge of +1; what is it?

Answer 16

A proton.

Question 17

A subatomic particle has a mass of 0 amu and a charge of -1. What is it?

Answer 17

An electron.

Question 18

How many energy levels (or “rings” in Bohrian language), does an atom of Calcium (Ca) have?

Answer 18

Four.

Calcium is in period 4 of the periodic table so it has 4 energy levels.

Question 19

How many electrons do atoms from group 1 have in their valence shell?

Answer 19

One electron.

Question 20

What is significant about the number of valence electrons for atoms in group 18, the noble gases?

Answer 20

Elements in group 18 have a full outer shell, so they will not react in chemical reactions.

Question 21

What do the elements Be, Mg, and Ca have in common?

Answer 21

They are in the same group and therefore

have the same number of valence electrons and therefore

behave the same way in a chemical reaction by losing two electrons.

Question 22

What is true of the number of valence electrons as you progress across the periodic table from left to right?

Answer 22

They increase.

Question 23

What is true of the number of valence electrons as you progress from top to bottom in the same group?

Answer 23

They remain the same.

Question 24

An atom which has lost or gained electrons to have a full outer shell is called

Answer 24

An ion.

Question 25

A sodium atom which has lost 1 electron is called a sodium ---.

Answer 25

Ion.

Question 26

Which is more **stable**, an oxygen atom or an oxygen ion?

Answer 26

An oxygen ion because it has a full valence shell.

Question 27

How does the valence shell of a Nitrogen atom change when it becomes a Nitrogen ion?

Answer 27

It **gains 3** electrons.

Question 28

What change happens to the valence shell of a Lithium **atom** when it becomes a Lithium **ion**?

Answer 28

It **loses 1** electron.

Question 29

What change to the valence shell would make a chlorine atom more stable?

Answer 29

**Gaining 1** electron.

Question 30

What change to the valence shell of Barium (Ba) would make it more stable?

Answer 30

**Losing 2** electrons.

Question 31

An element in group 18 will not react because

Answer 31

it has a **full** outer shell.

Question 32

Describe the reaction a Calcium atom will have with two chlorine atoms.

Answer 32

The calcium atom has two valence electrons; the chlorines each need 1, so the calcium will give 1 electron to each chlorine and together the 3 ions become a compound. **CaCl₂**

Question 33

Describe how the compound NaCl forms from its elements Na and Cl

Answer 33

An atom of Sodium (Na) has 1 valence electron which it gives to an atom of Cl, which needs 1 to fill its valence shell. The two are attracted together as ions, forming the compound NaCl.

Question 34

What is a "free radical?"

Answer 34

A free radical is a molecule which does not have a full outer shell of electrons. As a result, it steals an electron from other molecules to fill its shell, thus destroying the stability of the other molecule, thus creating a new free radical.

Question 35

Why are free radicals dangerous to living systems?

Answer 35

They create chain reactions of destruction for all kinds of molecules used in living systems. As they steal an electron, destroying one molecule, that molecule, in turn, destroys another. This interrupts very important chemical processes in cells.

Question 36

What is one way in which arsenic acts as a poison to living systems?

Answer 36

Arsenic creates free radicals.

Question 37

The atomic number on the periodic table will always indicate the number of which subatomic particle?

Answer 37

The number of protons.

Question 38

The atomic mass on the periodic table can be used to determine **what** concerning the subatomic particles?

Answer 38

The atomic mass indicates the **sum of the protons and neutrons**.

Question 39

What does the dot structure of a Calcium atom look like?

Answer 39

Question 40

Is the following dot structure an oxygen atom or an oxygen ion?

Answer 40

An oxygen **ion** because it has gained two electrons to fill its valence shell.

Question 41

Which of the following is the proper way to write the symbol for the element sodium? NA N_A Na

Answer 41

**Na**

Question 42

What is the maximum number of electrons which can be held by the first energy level?

Answer 42

**2**

Question 43

For practical purposes, how many electrons can be held by the energy levels 2 and above?

Answer 43

**8**