A&P - 2.1 Elements and Atoms: the building blocks of matter

chemistry

the science that studies that structure of matter

matter

• anything that takes up space and has mass

• the physical substance that makes up everything in the universe

mass

• the amount of material in matter - amount of matter in an object and is constant

• determines that weight of an object

• not the same a weight

• example: a person has the same mass on Earth and the moon, but their weight will be less on the Moon due to weaker gravity

types of matter

• solids = maintain their volume and their shape in ordinary temperature and pressures

• liquids = maintain a constant volume but no fixed shape

• gases = do not maintain a constant volume or fixed shape

what is matter composed of

one or more types of substances called elements

element

• substance that cannot be created or broken down by ordinary chemical means

• an element is a pure substance if it only consist of one type of atom

elements that are most abundant in the human body

• oxygen (65%)

• carbon (18.6%)

• hydrogen (9.7%)

• nitrogen (3.2%)

• calcium (1.5%)

atom

• the smallest invisible unit of an element and are therefore the smallest stable units of matter

• everything around us is composed of atoms in varying combinations

• atoms are composed of subatomic particles

nucleus

• center of atom

• contains one or more protons (may contain neutrons as well)

atomic mass

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

subatomic particles an atom is composed of

• protons

• neutrons

• electrons

protons

• single positive (+) charge

• mass = 1 atomic mass unit (amu)

• found in the atoms nucleus

neutrons

• no charge (neutral)

• mass = 1 amu

• found in the atoms nucleus

electrons

• single negative (-) charge

• very low mass

• found orbiting that atom’s nucleus

electron cloud

the electrons of the atoms whirl rapidly around the nucleus, creating and electron cloud (concentric clouds)

electron shell

• area of space a given distance from an atom’s nucleus in which electrons are grouped

• electrons are often shown in a fixed orbit around the nucleus called an electron shell (distinct levels of energy)

• in planetary model

• first shell like 2 electrons, when more than 2 electrons start on the next shell - after the first shell each shell after that wants 8 electrons

• shell closest to the nucleus contains the electrons with the least amount of energy and the energy in each electron increases as shells are farther away from nucleus

valence electrons

• orbit in the outermost shell of an atom (valence shell)

• with valence electrons the atom wants to bond with something that needs an electron so it can “donate” it and become positive while the atom the electron was “donated” to becomes negative (electron will go to whichever atom is closer to filling the electron shell)

atomic number

• the number of protons in the atom

• elements are listed in the periodic chart in order of their atomic number

neutral atom

• atoms that posses the same number of protons and electrons (no charge)

• can’t become an ion because there is no charge

isotopes

• varieties of an element that differ only in the number of neutrons in the nucleus

  • extra neutrons increase atomic weight

  • isotopes of an element have essentially identical chemical properties because they have the same number of valence electrons

• all atoms of the same element possess a constant number of protons in nucleus and electrons in shells

radioactive isotopes

unstable, heavy isotope that gives off subatomic particles, or electromagnetic energy, as it decays; also called radioisotopes