Molecules, Isotopes, Allotropes and chemical bonds

Question 1

Which elements are diatomic?

Answer 1

Hydrogen (H), Nitrogen (N), Oxygen (O), Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I)

Question 2

What is an allotrope in chemistry?

Answer 2

An allotrope is a different form of an element. An example is O2 is the standard form, but O3 (ozone) is an allotrope of oxygen.

Question 3

How is average atomic mass calculated?

Answer 3

Average = (Mass of Isotope * Percentage of that isotope found) + (repeat this process for all other isotopes)

Question 4

What are isotopes?

Answer 4

Isotopes are versions of an element with varying numbers of neutrons (Egs: Carbon-12 (6 neutrons) and Carbon-13 (7 neutrons))

Question 5

What is a bond in chemistry?

Answer 5

A chemical bond is an attraction between two atoms, often seen as different behaviours from the valence electrons.

Question 6

What is the difference between a polar and non-polar covalent (molecular) bond?

Answer 6

In a polar covalent bond, that means that the electrons are being shared unequally between the two elements. The electronegativity difference has to be over or equal to 0.5
In a non-polar covalent bond, that means that the electrons are being shared equally between the two elements. The electronegativity has to be less than 0.5

Question 7

What is the electronegativity level of hydrogen?

Answer 7

2.1

Question 8

What is the electronegativity level of boron?

Answer 8

2.0

Question 9

What is the electronegativity level of carbon?

Answer 9

2.5

Question 10

What is the electronegativity level of nitrogen?

Answer 10

3.0

Question 11

What is the electronegativity level of oxygen?

Answer 11

​3.5

Question 12

What is the electronegativity level of fluorine?

Answer 12

4.0

Question 13

What is the electronegativity level of chlorine?

Answer 13

3.0

Question 14

What is the electronegativity level of bromine?

Answer 14

2.8

Question 15

What is the electronegativity level of iodine?

Answer 15

2.5

Question 16

How is an ionic bond formed?

Answer 16

Let’s take lithium and fluorine as an example.
Lithium has one valence electron, fluorine has 7 valence electrons. Since fluorine has a high electronegativity (4) (due to it needing to satisfy the octet rule) and lithium has a low electronegativity (0.98), lithium likes to give up it’s valence electron to fluorine. When this occurs, lithium becomes a cation and fluorine becomes an anion, positives and negatives attract thus making an ionic bond.

Question 17

How is a non polar covalent bond formed?

Answer 17

Let’s take Bromine as an example.
Bromine is a diatomic atom and bromine has 7 valence electrons. When two bromine atoms meet, they both give one electron to each other, thus making a bond, solving the octet rule (they both have an additional electron in their bond)

Question 18

How is a polar covalent bond formed?

Answer 18

Let’s take carbon and oxygen as an example
Carbon has 4 valence electrons, oxygen has 6. Carbon gives up 2 and oxygen gives up 4, creating a triple bond, thus solving the octet problem (in each bond, they share two electrons and they both have 2 valence electrons). But since it’s a polar bond, they have an uneuqal share of electrons since oxygen has a significantly higher electronegativity (3.5 vs 2.5), thus oxygen will have more electrons towards them. In this case, it also makes oxygen have a partial negative charge and carbon have a partial negative charge.

Question 19

​How do display a partial charge?

Answer 19

δ^+ or δ^-