Chapter 2 Flashcards
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
Single bond
A pair of shared electrons
Double bond
Sharing two pair of valence electrons
Valence
The bonding capacity of unpaired electrons required to complete the outermost valence shell.
Matter
Anything that takes up space and had mass
Electronegativity
The attraction of a particular atom for the electrons of a covalent bond
Nonpolar covalent bond
In a covalent bond between two atoms of the same element, the electrons are shared equally.
Polar covalent bond
An atom bonded to a more electronegative atom, the electrons are not shared equally.
Oxygen is one of the most electronegative elements
Ion
A charged atom or molecule
Cation
Positive charged atom or molecule
Anion
Negative charged molecule
Ionic bond
Bond formed by the attraction between cations and anions.
Ionic compounds or salts
Compounds formed by ionic bonds
Hydrogen bond
The noncovalent attraction between hydrogen and an electronegative atom
Weak
Van see waals interactions
Are individually weak attractions and only occur when atoms and molecules are very close together. There are ever-changing regions of positive and negative charges that stick to one another.
Reactants
Starting material in the chemical reactions
Chemical reactions
The making and breaking of chemical bonds leading to changes in the composition of matter
Products
End result in a chemical reaction
Chemical equilibrium
The point at which the reactions offset one another exactly
