The Chemistry of Life: Chemical Elements

Matter

anything that has mass and takes up space (solid, liquid, gas, plasma)

Matter is composed of basic substances called...

elements

Element

composed of one atom, a subtance that cant be broken down into substances with different properties,

The 6 elements that make up 95% of the body weight of organisms

(acronym CHNOPS) Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur

The 3 elements all macromolecules have

Carbon, Hydrogen, and Oxygen

Phosphorus is found where?

DNA, RNA, Nucleic Acids

Sulfur is found where?

Occasionally proteins

Atom

smallest part of an element

proton

positive charge, in central nucleus

Neutrons

no charge, in central nucleus

Electrons

Negative charge, very low mass, in electron shells

electron shells

orbiting clouds around nucleus

Atomic number

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

mass number/atomic mass

the sum (+) of the number of protons and neutrons in the nucleus of an atom

Periods (periodic table)

Horizontal rows, elements in the same row have the same number of shells

Groups

Vertical columns on the periodic table, elements in the same group have the same valence and similar chemical properties

Atoms in the periodic table being electrically neutral means..

the atomic number tells you the number of electrons and protons

Isotopes

atoms that are the same (same element) but have different atomic masses

Radioactive Isotopes

give off energy in the form of rays and subatomic particles, ex Carbon 14 (used to examine photosynthesis reactions)

Four elements that make up 96% of living matter

carbon, hydrogen, oxygen, nitrogen

Four elements that make up remaining 4% of living matter

phosphorus, calcium, sulfur, potassium

Valence shell

outermost energy shell of an atom, determines many of an atoms chemical properties

octet rule

states that the outermost shell is most stable when it has 8 electrons

excpetion to the octet rule

if an atom only has one shell, the outermost valence shell us complete when it had two electrons, (Hydrogen, only has 1 shell)

atoms that have their valence shells filled with electrons tend to be...

chemically stable

atoms that do not have their valence shells filled with electrons tend to be...

chemically reactive

Effect of electrons on atom

they determine its chemical behaviors using the number of electrons in the atoms outermost shell (valence shell), like if it will share electrons with another atom

What tendency drives chemical reactions and creates bonds?

Atoms tendency to either complete a partially filled valence shell or empty a partially filled valence shell

Hydrogen bond

weak, attraction between + and -

Hydrophobic bonds

weak, no charge (non polar), repels/doesnt mix with water

Hydrophilic bonds

weak, polar (- or + charge), reacts/mixes with water

Covalent bonds

Strong, very stavke bonds formed by sharing electron pairs so there are 8 between them, forms molecules. ex. hydrogen gas

The more electrons shared in a covalent bond...

the stronger it gets

Nonpolar covalent bond

pair of electrons shared equally by 2 atoms (ex methane)

Polar covalent bond

electrons are shared unequally, ex water

electronegativity

the ability of an atom ot attract electrons towards itself in a chemical bond

Why are the bonds in water polar?

because the oxygen atom is more electronegative than the hydrogen atoms