ED: ch 2

Question 1

Name the four chemical elements that make up around 96% of living matter.

Answer 1

CHON

Question 2

how are some other elements are essential to life, despite their low prevalence in living organisms.

Answer 2

-Fe is involved in chlorophyll production, deficiency of it causes yellowing of plant
-Symptom of Iodine Deficiency
Enlargement of the thyroid gland,(Goiter) Thyroid hormones control metabolism and development
-Fe deficiency in animals causes Anemia (low red blood cell count)

Question 3

what is atomic number

Answer 3

proton number

Question 4

what is mass number

Answer 4

total number of protons and neutrons in the nucleus of an atom.

Question 5

what is atomic weight

Answer 5

atomic mass is the mass of an atom

where 1 dalton is defined as ​¹⁄₁₂ of the mass of a single carbon-12 atom,

Question 6

what are isotopes

Answer 6

same proton number different neutron number/ same atomic number different mass number

Question 7

what are radioactive isotopes

Answer 7

nucleus decays spontaneously, giving off particles and energy.

Question 8

what are the uses of radioactive isotopes

Answer 8

used to destroy cancer cells and as tracers to tract substances trough the body to identify (diagnose) cancer and other diseases and for Carbon-14 dating

Question 9

how can an electron move up/down a shell?

Answer 9

gain/lose energy

Question 10

which shell has the most amount of energy?

Answer 10

valence shall

Question 11

what is the max number of electrons that shell 1 and 2 can hold?

Answer 11

1= 2e

2=8e

Question 12

what is the chemical behaviour of an atom determined by?

Answer 12

distribusion of electrons in its electron shells

Question 13

state the chemical bonds strongest to weakest

Answer 13

1- covalent
2- ionic
3-h-bonds
4- Van der Waals interactions

Question 14

what are the two ways atoms can fill their valence shell

Answer 14

by sharing electrons with another atom like in covalent bonding or it can completely transfer electrons like in ionic

Question 15

what is electronegativity?

Answer 15

The ability of an atom to attract electrons in a chemical bond to itself.

Question 16

Non-polar vs Polar covalent bonding and exceptions

Answer 16

• A covalent bond is non-polar if both atoms are the same and equally electronegative
• A covalent bond is polar if one of the atoms is more electronegative – Electrons of a polar covalent bond are pulled closer to the more electronegative atom

-Electronegativity difference BUT the molecule is symmetric, therefore the dipoles cancel out

Question 17

describe ionic bonding

Answer 17

A positively charged ion is called a cation, while a negatively charged ion is called an anion. Because of their opposite charges, cations and anions attract each other; this attraction is called an ionic bond.

-cation loses e, anion gains e

Question 18

why is ionic bonding weaker in biology?

Answer 18

most biological reactions take place in water and ionic bonds are able to break down in water

Question 19

What is h-bonding?

Answer 19

Weak attraction between one electronegative atom (F,N,O) and a hydrogen atom that is linked to another electronegative atom

Question 20

what are Van der Waals interactions?

Answer 20

Non-polar molecules have transient positively and negatively charged region because electrons are in constant motion and some of the time the electrons may be distributed asymmetrically causing one region to be +ve or -ve and to attract and interact with the opposite charge temporarily

Question 21

What is a chemical reaction?

Answer 21

The making and breaking of chemical bonds, leading to changes in the composition of matter

Question 22

what is a chemical equillibrium?

Answer 22

• chemical equilibrium is the state in which both reactants and products are present in concentrations which have no further tendency to change with time, so that there is no observable change in the properties of the system.
• No net effect on the concentrations of reactants and products

Question 23

what is one of the factors affecting the rate of a reaction

Answer 23

The greater the concentration of reactant/products molecules, the more frequently they collide with one another and have an opportunity to react and form products/reactants.