Ch. 2.1 Chemistry Intro

Question 1

Atomic Mass

Answer 1

Equal to the number of protons plus neutrons

Question 2

Atomic Number

Answer 2

The number of protons

Question 3

Atom

Answer 3

Smallest unit of an element.

• Nucleus with positively charged protons and uncharged neutrons
• Orbiting electrons with negative charges

Question 4

Chemical bonds

Answer 4

• Chemical bonds are formed when electrons in atoms interact.
• The number of bonds an atom can form is determined by the number of valence electrons.

Question 5

Electron Orbital Shells

Answer 5

Energy levels that surround the nucleus of an atom. Electrons fill the shells, starting with the one closest to the nucleus.

Question 6

Valence Electrons

Answer 6

Electrons in unfilled outer shells that participate in bonding

Question 7

Covalent Bonds

Answer 7

Occurs when valence electrons are shared because energy levels overlap.

Question 8

Nonpolar Covalent Bond

Answer 8

Electrons are shared equally.

i.e. - 2 hydrogen atoms

Question 9

Polar Covalent Bond

Answer 9

Electrons that are not shared equally. They have positive and negative ends.
i.e. – between oxygen and hydrogen in water

Question 10

Significance of Water (H2O)

Answer 10

1) Polar molecule
2) Good solvent (substances dissolve in it)
3) Can form strong hydrogen bonds
4) Polar molecules (covalent bonds) may dissolve in water and are called hydrophilic
5) Nonpolar molecules do not dissolve in water and are called hydrophobic

Question 11

Ionic Bonds

Answer 11

One atom gives electrons to another so that both have filled valence shells.

• Cations and anions attract each other to form ionic compounds
• Individual ionic bonds are weaker than covalent bonds

Question 12

Cation

Answer 12

An electron donor in ionic bonds; positively charged

Question 13

Anion

Answer 13

An electron receiver in ionic bonds; negatively charged

Question 14

Ionic Bonds and Water

Answer 14

Most ionic bonds dissolve in water

1) The negative side of water is attracted to the cation, and the positive side of water is attracted to the anion.
2) This is a strong attraction that pulls the ions apart

Question 15

Hydration Spheres

Answer 15

Water molecules that have surrounded ions

Question 16

Hydrogen bond

Answer 16

Weak bond formed between two polar molecules based on opposite charges attracting (not based on electron sharing)

i. e. -
1. ) Forms between electropositive H atoms and electronegative O or N atoms
2. ) Forms between water molecules; responsible for surface tension and capillarity
3. ) Forms between amino acids on a protein to produce the 3D structure of the protein
4. ) Holds the two strands of the DNA molecule together.

Question 17

pH Scale

Answer 17

A way of measuring hydrogen ions (H+ concentration) to test how acidic or alkaline a solution is.

• Runs from 0-14
• 0 is the strongest acid, 14 is the strongest base

Question 18

Base (Alkaline)

Answer 18

• When a solution has more OH- ions than H+ ions
• pH is above 7
• Often called a proton acceptor

Question 19

Acid

Answer 19

• When a solution has more H+ ions than OH- ions
• pH is below 7
• Often called a proton donor

Question 20

Neutral pH

Answer 20

• When there are the same number of H+ ions as OH- ions in solution.
• A neutral solution is said to have a pH of 7 (which means 10-7 molar concentration H+).

Question 21

Buffers

Answer 21

• Stabilize pH in a solution.

- Has 2 components – a weak acid and a weak base (buffer pair)

Question 22

Acidosis

Answer 22

If blood falls below pH 7.35

Question 23

Alkalosis

Answer 23

If blood rises above pH 7.45