CHAPTER 2: ENERGY/ATOMS

matter

has mass and occupies space. solid, liquid and gas

mass

means weight

element

every single one has atomic number, element symbol, and atomic mass number

major elements

collectively compose almost 99% of body weight

what are the major elements

oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus

minor elements

collectively compose less than 1% of body weight

what are the minor elements

sulfur, potassium, sodium, chlorine, magnesium and iron

subatomic particles

neutrons, protons and electrons

neutrons

no charge, weigh one atomic mass unit

protons

positive charge, weigh one atomic mass unit

electrons

negative charge, almost no weight

atomic number

number of protons in an element, same as proton number

atomic mass

weight of both protons and neutrons

nucleus

in the middle, containing neutrons and protons

energy shell

where electrons are located and each shell has a set number

innermost shell

holds 2 electrons max

second shell

holds 8 electrons max

isotopes

different atoms of the same element, same number of protons and electrons but different number of neutrons

radioisotopes

contains excess neutrons and becomes unstable

half life

what it takes to get rid of half the amount

biological half life

the time it takes for half of the radioactive material from a test to get out of our body

valence electrons

electrons based on group number from periodic table

octet rule

desire for elements to want 8 electrons

chemical compound

combine 2 or more elements in a fixed ratio

cations

ions with a positive charge, lose electrons

anions

ions with a negative charge, gain electrons

ionic bonds

cations and anions bounded by electrostatic forces

covalent bonded molecule

electrons shared between atoms of 2 or more different elements

isomers

same number and type of elements but arranged differently in space

hydrogen

1 electron & bond

oxygen

2 electrons & bonds

nitrogen

3 electrons & bonds

carbon

4 electrons & bonds

electronegativity

relative attraction of each atom for electrons

nonpolar covalent bond

two atoms of the same element have equal attraction for electrons

polar covalent bond

sharing of electrons unequally

greatest to least electronegativity

oxygen, nitrogen, carbon, and hydrogen (ONCH)

amphipathic molecules

big molecules with both polar and nonpolar regions, one polar and one nonpolar head

intermolecular attraction

weak chemical attractions between molecules

hydrogen bond

attraction between partially positive hydrogen atom and a partially negative atom

example of hydrogen bond

positive hydrogen bonding with negative oxygen