biology

elements

a pure substance that cannot be broken down into other substances

what are the four elements?

oxygen, carbon, hydrogen, nitrogen

how much living matter in the body do elements make up

96% of the human body

trace elements

needed for the body in small amounts. insufficient amounts can cause health issues

compounds

a substance containing 2 or more elements that are chemically combined in a fixed ratio

list the four most abundant elements in your body

oxygen 65%, carbon 18.5%, hydrogen 9.5%, nitrogen 3.3%

how are elements and compounds different?

elements are individual while compounds are multiple elements

atoms

smallest possible particle of an element

what are the 3 subatomic particles and what are the charges

protons- positively charged. electron- negatively charged. neutron- no charge

where are protons and neutrons located

in the nucleus

where are electrons located

they move around the nucleus

atomic number

the number of protons in an atoms nucleus

isotopes

alternate form of an element. they have the same number of protons but different electrons

radioactive isotopes

has a nucleus that decays or breaks down. used in research and medicine. releases radiation in the form of matter and energy

most often the electrons in the highest energy level…

determine how the atom reacts

how many electrons are in the 4 elements

H- 1 electron. C- 6 electrons ( 4 in 2nd lvl.) N- 7 electrons (5 in 2nd lvl). O- 8 electrons ( 6 in 2nd lvl)

partially filled energy levels result in?

chemically reactive atoms

atoms that are fully filled…

are not chemically reactive

chemical bonds..

join atoms to one another

ionic bonds

chemical bonds that are formed when 1 atom transfers an electron to another atom

covalent bonds

forms when 2 atoms share electrons

what are the number of bonds

the number of bonds an atom can form tends to equal the number of electrons it needs to fill its highest energy lvl

molecules

formed by 2 or more atoms joined by covalent bonds

chemical formula

shows the type and number of atoms in a molecule

methane

CH4

propane

C5 H8

butane

C4 H10

chemical reactions

involve breaking or forming chemical bonds

chemical equations

used to describe reactions. shows reactants and products

how is potassium atom different from potassium ion

the ion has lost an electron giving it a positive charge