AP Biology - Unit 0

Chapters 2 and 3

Matter

Anything that takes up space and has mass

Element

A substance that can’t be broken down to other substances by chemical reactions

Compound

A substance that consists of 2 or more different elements in a fixed ratio

What four elements make up of 96% of all living matter?

Hydrogen, Carbon, Oxygen, Nitrogen (HCON)

Essential Element

Elements needed for organisms to live a healthy life (ex. HCON)

Trace Element

Elements that are needed in small quantities (ex. Iron/Fe)

Model of Helium (including the electrons, protons, neutrons, and atomic nucleus)

Atomic Number and Atomic Mass of Helium

2, 4

Neutron

Subatomic particle with no electric charge (in the nucleus)

Proton

Subatomic particle with a positive charge (in the nucleus)

Electron

Subatomic particle with a negative charge (orbits the nucleus)

Atomic Number

Number of protons

Atom

Smallest unit of matter that still has the properties of an element

Atomic Mass

Total mass of an single atom

Isotope

Different form of an element (same number or protons, different number of neutrons)

Electron Shells

Region surrounding the nucleus of an atom where electrons are found

Energy

The capacity to cause change (ex. doing work)

1. What is the atomic mass?

2. What is the atomic number

3. How many electrons?

4. How many neutrons?

1. 12

2. 6

3. 6

4. 12

1. How to calculate mass number?

2. Atomic number?

3. Neutrons?

1. Protons + Neutrons

2. Protons or Number of Electrons in Neutral Atom

3. Mass Number - Atomic Number

Which is the only subatomic particle that is directly involved in the chemical reactions between atoms?

Elections

What is potential energy?

Energy that matter processes because of its location or structure

Explain which has more potential energy in each pair:

1. Boy at the top of a slide/boy at the bottom

2. Electron in the first energy shell/electron in the third energy shell

3. Water/glucose

1. Boy at top

2. Third shell

3. Glucose (larger and more complex structure)

What determines the chemical behavior of an atom?

Distribution of electrons in the atom’s electron shells (mostly on the outmost shell)

Molecule

2 or more atoms held together by covalent bonds (2 nonmetals)

Covalent Bond

Sharing of electrons

What type of bond is seen in O2? Explain what this means.

Double bond, sharing of 2 pairs of valence electrons (1 pair = 2 valence electrons)

Electronegativity

The ability of an atom to attract other electrons in a chemical (covalent) bond

Explain the difference between a non polar covalent bond and a polar covalent bond

Nonpolar = electrons are equally shared (atoms have equal electronegativity)

Polar = electrons are unequally shared (one atoms is more electronegative)

Make an electron distribution diagram of water. Which element is most electronegative? Label the regions that are more positive or more negative.

Oxygen is more electronegative (larger atomic nucleus with 8 protons).

More positive = Hydrogens

More negative = Oxygen

Why is water considered a polar molecule?

Water is polar because of the unequal sharing of electrons, Oxygen has a higher electronegativity than Hydrogen so electrons favor Oxygen. This gives Oxygen a slight negative charge and Hydrogen a slight positive charge.