Chapter 2 Flashcards
(42 cards)
Compound
A substance consisting of two or more different elements combined in a fixed ratio
NaCl
Element
Substance that can’t be broken down into other substances
92 elements ie gold, copper, silver
Essential elements
20-25% of the natural elements that an organism needs in order to lead a healthy life
Humans need 25
Plants need 17
Which four elements make up 96% of living matter?
Carbon (C)
Oxygen (O)
Hydrogen (H)
Nitrogen (N)
Trace elements
The remaining four percent of an organism’s mass (only needed in small or trace amounts)
Calcium (Ca)
Potassium (K)
Sulfur (S)
Atom
Smallest unit of matter that still retains the properties of an element
Subatomic particles
Proton positive
Electron negative
Neutron neutral
Atomic nucleus
Densely packed with protons and neutron at the core of an atom.
Protons give the nucleus a positive charge and electrons form an electron cloud outside of the nucleus.
Dalton
A unit of measurement for describing the mass of an atom (atomic mass unit or amu)
Atomic number
Number of protons for an element which is written as a subscript to the left of the element’s symbol
Mass number
The sum of protons plus neutrons in the nucleus of an atom
Written above the atomic number
Hydrogen
Simplest element and and has no neutrons
Atomic mass
Equals the atomic number (approximately ___ daltons)
Isotope
When the same element has varying numbers of neutrons
Most common isotope for carbon is 12/6 C
Radioactive isotope
Isotope that is unstable or loses particles
It’s nucleus decays spontaneously giving off particles and energy. When it changes its number of protons, it becomes another element.
14/6 C
Energy
The capacity to cause change
Potential energy
The energy matter possesses because of its location or structure
Ie water in a reservoir on a hill has potential energy because of its altitude
Electron shells
Determine the amount of energy an electron has - closer it is to the nucleus, the lower the potential energy.
When an electron loses energy in the form of heat, it falls back to a shell closer to the nucleus.
Valence electrons
Located in the outermost (valence) shell and determines the majority of the behavior of the atom.
Elements with the same number of valence electrons exhibit similar behavior. Ie chlorine and flourine
Inert atoms
Atoms with full valence shells don’t react with anything else chemically.
Helium
Neon
Argon
Orbital
Space where an electron is found 90% of the time
Chemical bonds
When atoms are held together by valence electrons (either sharing it transferring)
Strongest are ionic and covalent
Covalent bond
Sharing of a pair of valence electrons by two atoms
Molecule
Two or more atoms held together by a covalent bond
Ie H2
