The Chemical Context of Life

Question 1

Define an element

Answer 1

An element is a substance which cannot be broken down any further by chemical reactions

Question 2

Define a compound

Answer 2

A compound is a combination of two or more different elements

Question 3

What are the 4 essential elements of a living organism?

Answer 3

• CHON
  1) carbon
  2) hydrogen
  3) oxygen
  4) nitrogen

Question 4

What are trace elements?

Answer 4

Substances which are essential to organisms in only minute quantities

Question 5

Define subatomic particles and identify 3

Answer 5

Subatomic particles are the smallest units of an element. Elements are made up of atoms which are made up of these particles.

1) neutrons
2) electrons
3) protons

Question 6

What subatomic particles are found in the atomic nucleus?

Answer 6

protons and neutrons are tightly packed within the atomic nucleus

Question 7

Where are the electrons found in particles?

Answer 7

the electrons of an atom are rapidly moving around the nucleus in orbitals

Question 8

What is the mass number and the atomic number?

Answer 8

The mass number represents the total number of protons and neutrons found within the atomic nucleus

The atomic number represents the number of protons and the number electrons in a neutral atom

Question 9

How can one find the number of neutrons in an atom’s atomic nucleus?

Answer 9

Mass number - atomic number = # of neutrons

Question 10

What are isotopes? Provide an example

Answer 10

Isotopes are different forms of a certain atom in which there is a small difference in the atomic numbers.

ex. carbon-12, carbon-13, carbon-14

Question 11

What are radioactive isotopes?

Answer 11

Radioactive isotopes are those with an unstable atomic nucleus which spontaneously decay and give off particles and energy.

Question 12

How are radioactive isotopes used as a tool in medicine?

Answer 12

Radioactive isotopes can be used to track atoms during chemical processes and metabolism in an organism. They can be referred to as radioactive tracers.

Question 13

What is meant by the potential energy of an electron?

Answer 13

The potential energy of an electron is given by distance from the nucleus. Those that are further from the nucleus have more potential energy whereas those that are closer have less potential energy.

Question 14

What are valence electrons and a valence shell?

Answer 14

The outermost shell and electrons orbiting the atomic nucleus

Question 15

What is an orbital?

Answer 15

An orbital is a more accurate idea of where electrons spend 90% of their time while orbiting the nucleus

Question 16

Describe how electron orbitals may look and their characteristics

Answer 16

• each orbital may only hold up to 2 electrons in each orbital move at different rates
• consist of similar energy levels
• electrons in each
• the first orbital consists of 1 spherical s orbital
• the second orbital consists of 1 larger s orbital and 3 dumbell-shaped p orbital

Question 17

What does the electronegativity of an atom represent?

Answer 17

The electronegativity of an atom refers to the force of attraction between an atom and electrons

Question 18

what is the difference between polar and non-polar covalent bonds?

Answer 18

• a nonpolar covalent bond is one in which electrons are shared equally between each element. Each element of the bond consists of similar electronegativities.
• a polar covalent bond is one in which electrons are unevenly shared between elements of the bond as for different electronegativities. This creates partial charges at certain ends of the compound

Question 19

What are ions and how are they formed?

Answer 19

Ions are atoms with either a negative or positive charge. They are the result of electrons which have been completely stripped away from the pairs from which they were being shared.

Question 20

What is an ionic bond?

Answer 20

An ionic bond is a pair of ions which are bounded by the attraction of opposite charges.

Question 21

What is the difference between dry ionic compounds and those submersed in water?

Answer 21

While dry ionic compounds maintain the strength of the bond, when submerged in water, water molecules weaken the force of attraction between the opposite charges acting as a shield between the bonded ions

Question 22

What are some weak chemical reactions? explain.

Answer 22

• hydrogen bonds : weak non-covalent bonds between partially positive hydrogen and another electronegative atom with an opposite charge
• Vaan der Waals interactions: short-lasting simultaneous bonds formed between atoms of changing partial negative and positive charges. These interactions may only occur in close proximities

ex. london forces, dipole-dipole

Question 23

How is the molecular shape of an atom determined?

Answer 23

The molecular shape of an atom depends on the position of it’s orbitals

Question 24

What is a hybrid orbital?

Answer 24

When the valence shell orbital (2s+2p) combines, it forms a 4-tear-dropped shape which extends to all four corners known as a hybrid orbital. This type of orbital is connected to form a geometric shape known as a tetrahedron.

Question 25

What is a chemical equilibrium?

Answer 25

A chemical equilibrium is when there is no net change to the concentration of products and reactants. Both concentrations remain constant meaning both forward and reverse reactions are taking place at a consistent rate

Question 26

What is a concentration equilibrium?

Answer 26

When the concentrations of products and reactants have come to a steady ratio