Atoms and the Periodic Table

Question 1

Explain atomic mass.

Answer 1

The are the average masses calculated based on the mass and % abundance of the naturally occurring stable isotopes.

Question 2

Where was Dmitri Medelev born?

Answer 2

Siberia, Russia.

He invented the periodic table.

Question 3

What determines the identity of an atom?

Answer 3

The number of protons in its nucleus.

Also called the elements atomic number.

Question 4

What comprises almost 100% of an atoms volume?

Answer 4

The electron cloud.

If the nucleus was a grain of rice, the electron cloud would be the size of a football stadium.

Question 5

True or False:
A proton is attracted to a neutron.

Answer 5

False.

Neutrons don’t have an electric charge.

A proton is attracted to an electron.

Question 6

True or False:
The nucleus contains virtually all the mass of an atom.

Answer 6

True.

Electrons are so light they aren’t counted for.

Protons and neutrons both have a mass of 1.

Question 7

True or False:
Protons and electrons have opposing charges.

Answer 7

True.

Opposing charges attract one another.

Question 8

State the subatomic particle that matches the description:

1. Has virtually no mass.
2. Has a positive charge (+1).
3. Is electrically neutral.
4. Particles that make up most of the nucleus.

Answer 8

1. Electrons.
2. Protons.
3. Neutrons.
4. Protons and neutrons.

Question 9

Gallium has 2 isotopes. 60.4% is Ga-69 (mass = 68.9257 amu), and 39.6% is Ga-71 (mass = 70.9248 amu).

Calculate the atomic weight for gallium.

Answer 9

Rounded and proper significant figures.

69.7 amu

Question 10

If an atom has 28 protons and A = 60.

Identify:

How many electrons does it have?
How many neutrons does it have?
What element is the atom from?

Answer 10

It has 28 protons and electrons.

If A = 60 neutrons = ?

60 - 28 = 32.

It would have 32 neutrons.

of protons = atomic # … therefore the element is nickel.

Question 11

Which atom is bigger, Na or Cl?

Answer 11

Na is bigger.

Nuclear charge rises from left to right in a period.

Since the electronegativity increases, as does the attraction to the valence electrons. This causes the atoms size to shrink.

Question 12

What atom is larger, Rb or Na?

Answer 12

Rb is larger.

Generally the atomic radius increases as we move down the groups.

Rb is below Na, thus we would expect it to be larger.

Question 13

Place the elements in order of decreasing atomic size:

Cl, Br, I.

Answer 13

I, Br, Cl.

Because I is the lowest, it would actually be the biggest.

Bottom left biggest, the more up an right you move, the smaller the atoms get.

Question 14

Which group on the periodic table are highly reactive, silvery, soft metals?

Answer 14

Group 1 (Alkali metals).

Groups = columns.

Periods = Rows

Remember: periods have to have a period at the end like a sentence.

Question 15

Which group on the periodic table are colorful and reactive non-metals?

Answer 15

Group 7 (Halogens).

Question 16

Which group on the periodic table are chemically invert, colorless gasses?

Answer 16

Noble gasses.

They have no reactions.

Ne, He, and Ar do not combine with anything.

Question 17

Write out the electron configuration of magnesium.

Answer 17

Mg = 12 electrons.

1s2, 2s2, 2p6, 3s2.

or… Mg = [Ne] 3s2.

Ne is the preceding noble gas.

Question 18

Write the electron configuration of phosphorus (z = 15).

Answer 18

1s2, 2s2, 2p6, 3s2, 3p3.

or… [Ne] 3s2, 3p3.

Question 19

What is the maximum # of electrons that occupy the 4th shell?

Answer 19

32 electrons.
________________________
1st shell = 2 electrons
2nd shell = 8 electrons
3rd shell = 18 electrons
4th shell = 32 electrons

Question 20

What is the maximum electrons that can occupy the 3d shell?

Answer 20

10 electrons because each orbital can carry 2 electrons, and d have 5 orbitals.
___________________
s = 1 orbital; 2 max. electrons
p = 3 orbitals; 6 max. electrons
d = 5 orbitals; 10 max. electrons
f = 7 orbitals; 14 max. electrons

Question 21

What is the electron configuration of carbon?

Answer 21

C (z = 6)

1s2, 2s2, 2p2.
or
[He] 2p2.

Question 22

Which element has the following electron configuration?

1s2, 2s2, 2p6, 3s2.

Answer 22

Magnesium.

By counting how many electrons are on each energy level, you can use that electron number to find the atomic number.

Question 23

Which element group would be represented by the # of dots on the Lewis-dot diagram.

1. 6 dots.
2. 3 dots.
3. 2 dots.
4. 7 dots.
5. 8 dots.
6. 1 dot.

Answer 23

1. 6 dots = Group 6A
2. 3 dots = Group 3A
3. 2 dots = Group 2A (alkali earth metals)
4. 7 dots = Group 7A (halogens)
5. 8 dots = Group 8A (noble gasses)
6. 1 dot = Group 1A (alkali metals)

Question 24

Amphetamine, a commonly abused drug, is comprised of nine atoms of carbon, 13 atoms of hydrogen, and one atom of nitrogen.

How would you write the chemical formula of amphetamine?

Answer 24

C9H13N.

Question 25

An s-block element in the 5th period is:

A) Mo
B) Ag
C) As
D) Y
E) Sr

Answer 25

E) Sr

The s-block is group 1A and 2A.

To know the period count the rows from top to bottom beginning with the row H + He.

Question 26

An oxygen atom with a mass number of 18 has:

A) 8 protons, 8 electrons.
B) 10 protons, 8 neutrons.
C) 8 protons, 10 neutrons.
D) 8 neutrons, 10 protons.
E) 2 of these answers are correct.

Answer 26

E) 2 of these answers are correct.

A) 8 protons, 8 electrons.
C) 8 protons, 10 neutrons.

Question 27

Which element corresponds with the following electron configuration?

1s2, 2s2, 2p6, 3s2, 3p2.

Answer 27

Silicon.

Count the superscript to find how many electrons it has, then b/c p+ = e- = atomic # (z) …
the electron number is the z. (assuming its a neutral atom, not an ion).

Question 28

True or False:
Density = specific gravity.

Answer 28

True.

Because water is 1g/mL at normal temperatures, density = specific gravity.

Specific gravity has no units because they cancel out = g/mL.

Question 29

What are the units used for specific gravity?

Answer 29

Trick question! - There are no units for specific gravity because they cancel out.

Specific gravity = density g/mL /density of water 1g/mL.

Question 30

At normal temperatures, what is the density of water?

Answer 30

1 g/mL.

Question 31

If an element has 7 valence electrons, which group must it belong to?

Answer 31

It would belong to group 7, halogens.

of valence electrons = group number.

Question 32

How many orbitals does the ‘p’ subshell have?

What is the maximum electron number for the ‘p’ subshell?

Answer 32

The ‘p’ subshell has:

3 orbitals and can hold a maximum of 6 electrons.

Question 33

Which are the most reactive?

A) Halogens.
B) Noble gasses.
C) Alkali metals.
D) Alkali earth metals.
E) Transition metals.

Answer 33

C) Alkali metals.

Na is not found in nature because it explodes when it reacts with air or water.

Question 34

Which elements correspond to the ‘d-block’?

Answer 34

Transition metals.

Ex. Ti (z = 22).
1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d2.
or [Ar] 4s2, 3d2.

Question 35

Which elements correspond to the ‘s-block’?

Answer 35

Group 1A - 2A.

The valence shell of these elements will finish with a s orbital.

Example: H (z = 1) = 1s1.

Question 36

Which elements correspond to the ‘p-block’?

Answer 36

Elements in group 3A - 8A.

These elements electron configuration will have the p orbital as its valence shell.

Example: O (z = 8). 1s2, 2s2, 2p4.

Question 37

Why were noble gasses not known at the time of Mendelev?

Answer 37

Elements were discovered based on reactivity.

It was hard for scientists to work with them because they are so unreactive.