The atom and chemical bonds

Question 1

Two most common elements in biology

Answer 1

Carbon and Hydrogen

Question 2

Structure of the atom

Answer 2

The atom is made up of a nucleus at the centre and surrounding electrons in orbit.
There is always the same amount of electrons as there are protons.

Question 3

What is an Isotope?

Answer 3

An isotope is an unstable atom in which number of protons and neutrons is not the same.
This results in the same chemical properties but different physical properties.
Often isotopes with more neutrons are unstable (used in medicine)

Question 4

What makes up the nucleus?

Answer 4

The nucleus is made up of protons and neutrons. It makes up most of the mass of an atom.

Question 5

Why is the mass number in a periodic table never whole?

Answer 5

The mass number accounts for the isotopes of the atom.

Question 6

What are the 5 elements of life

Answer 6

Carbon
Hydrogen
Oxygen
Nitrogen
Phosphorus

Question 7

Describe a covalent bond

Answer 7

• Made up of 2 electrons that are shared
• Atoms are able to form bonds until their outer shell is full
• This is called a molecule

Question 8

What are the two types of covalent bonds? Describe them

Answer 8

• Non-polar covalent bond (electrons are equally shared)

- Polar covalent bonds (electrons are not shared equally)

Question 9

Describe a hydrogen bond

Answer 9

• Occurs between negatively charged oxygen and positively charged hydrogen
• Causes the formation of meniscus when meeting solid surface
• Explains high surface tension of water

Question 10

Why does ice float?

Answer 10

-Ice forms a crystal lattice; liquid water doesn’t.

Therefore, liquid water is denser than ice. This is why ice floats

Question 11

Describe an ionic bond and its two types

Answer 11

-Ionic bond is formed by the attraction of two oppositely charged ions
-Two types: Cation (positively charged)
Anion (negatively charged)

Question 12

Hydrophilic

Answer 12

“water loving” polar molecules and ions that dissolve readily in water

Question 13

Hydrophobic

Answer 13

“water hating” non-polar molecules and ions that do not dissolve in water
-Hydrophobic interactions only have power when lots of molecules are involved

Question 14

Van der waals interaction

Answer 14

Non-polar molecules also have a very weak attraction to each other via transient dipoles. (due to fluctuating electrical charges)

Question 15

Properties of Acids- when is it strong vs weak

Answer 15

Acids release/donate H+ ions in solution

• Weak acids (often carboxyl group) are so because they only dissociate partially and reversibly
• Strong acids (like HCl) are so because their reaction is complete

Question 16

Properties of Bases

Answer 16

• Accept H+ in solution and release (OH-)

- Strong bases are characterized by their ability to ionize completely

Question 17

The amino group- why is it important and is it weak or strong?

Answer 17

• NH2- important part of many biological compounds

- Functions as weak base by partially and reversibly accepting H+

Question 18

What is a buffer? How does it work?

Answer 18

A buffer makes overall solution more resistant to pH change.
This is because they function as both an acid and a base.
MUST be able to buffer in both directions

Question 19

Which bond is strongest: covalent or hydrogen?

Answer 19

Covalent in always stronger!