Biology Chapter 2

anything that takes up space and composed of elements

substance that can't be broken down

substance consisting of two or more elements in a fixed ratio

smallest unit of matter that still retains property of a element

no charge

positive

negative

2

8

8

18

protons and neutrons

Proton mass (daltons)

capacity to cause change

energy matter has because of it location or structure

electron's state of potential energy

outermost shell and hold the valence electrons

Inert or Noble gases

3D space where an electron is found 90% of the time

bonding capacity of an atoms

2 or more atoms share/donate/accept electrons to form molecules and compounds

sharing of electrons

two or more atoms held together by covalent bond

sharing of one pair of valence electrons

sharing of two pairs of valence electrons

• atoms attraction for the electron in a covalent bond
• **the more electronegative an atom, the stronger it pulls shared electrons towards itself**

atoms share electrons EQUALLY

one is more electronegative (not shared equally)

charged atom

positively charged ion

negatively charged ion

attraction between anion and cation forming Ionic compounds (salts)

hydrogen atom covalently bonded to a electronegative atom is also attracted to another electronegative atom

making and breaking of chemical bonds

starting molecules of chemical reactions

final molecules of a chemical reaction

when the forward and reverse reaction rates are equal

required by an organism

• Carbon
• Hydrogen
• Oxygen
• Nitrogen

• Calcium
• Phosphorus
• Potassium
• Sulfur

# of proton

sum of protons AND neutrons

approximately mass number (number off periodical table)

two atoms of an element that differ in number of neutrons

H-H

H²O

H:H