Lecture 3 Chemistry

Question 1

Element

Answer 1

A substance that cannot be broken down into substances with different properties; composed of one type of atom

Question 2

Fun Fact!

Answer 2

There are only 92 naturally occurring elements in the universe, the rest are man made

Question 3

Atom

Answer 3

The smallest part of an element that displays the property of the element

Question 4

Proton

Answer 4

Positively charged, 1 amu (atomic mass unit)

Question 5

Neutron

Answer 5

No charge, 1 amu

Question 6

Electron

Answer 6

Negatively charged, very low mass-negligible in calculations

Question 7

Atomic Number

Answer 7

equal to the number of protons in each atom of an element

Question 8

Mass Number

Answer 8

atom is equal to the sum of the number of protons and neutrons in atom’s nucleus

Question 9

Atomic Mass

Answer 9

approximately equal to the mass number

Question 10

Periods

Answer 10

arranged horizontally by increasing atomic number in rows called

Question 11

Groups

Answer 11

Atoms of an element arranged in vertical columns are called

Question 12

Isotopes

Answer 12

atoms of the same element that differ in the number of neutrons (and therefore different atomic masses)

Question 13

The Distribution of Electrons

Answer 13

Bohr model

Electrons revolve around the nucleus in energy shells (energy levels).

For atoms with atomic numbers of 20 or less, the following rules apply:

• the first energy shell can hold up to 2 electrons
• each additional shell can hold up to 8 electrons
• each lower shell is filled first before electrons are placed in the next shell

Question 14

Valence Shell

Answer 14

outermost energy shell

Question 15

Molecule

Answer 15

Two or more elements bonded together

Question 16

Compound

Answer 16

a molecule containing at least two different elements bonded together

Question 17

Formula

Answer 17

tells you the number of each kind of atom in a molecule

Question 18

Ion

Answer 18

an atom that has lost or gained an electron

Question 19

Ionic bond

Answer 19

forms when electrons are transferred from one atom to another atom and the oppositely charged ions are attracted to one

Question 20

Covalent Bonds

Answer 20

when two atoms share electrons so each atom has an octet of electrons in the outer shell

Question 21

Nonpolar Covalent Bond

Answer 21

electrons are shared equally between atoms.

Examples: hydrogen gas, oxygen gas, methane

Question 22

Electronegativity

Answer 22

the ability of an atom to attract electrons towards itself in a chemical bond. Electronegativity is based on the number of protons-the greater the number of protons, the greater the electronegativity

Question 23

Hydrogen Bond

Answer 23

a weak attraction between a slightly positive hydrogen atom and a slightly negative atom

Question 24

Properties of Water

Answer 24

Water has a high heat capacity

Water has a high heat of vaporization

Water is a good solvent

Water molecules are cohesive and adhesive

• Cohesion is the ability of water molecules to cling to each other due to hydrogen bonding
• Adhesion is the ability of water molecules to cling to other polar surfaces

Question 25

Hydrophilic & Hydrophobic

Answer 25

* Hydrophilic molecules dissolve in water. | * Hydrophobic molecules do not dissolve in water.

Question 26

Ph

Answer 26

a measure of hydrogen ion concentration in a solution

Question 27

Acids

Answer 27

substances that dissociate in water, releasing hydrogen ions

Question 28

Bases

Answer 28

substances that either take up hydrogen ions (H+) or release hydroxide ions (OH−)

Question 29

Ph scale

Answer 29

``` Used to indicate the acidity or basicity (alkalinity) of a solution. •Values range from 0-14 •0 to <7 = Acidic •7 = Neutral •>7 to 14 = Basic (or alkaline) ```

Question 30

Buffer

Answer 30

a chemical or a combination of chemicals that keeps pH within normal limits