Chapter 2 Flashcards
Matter
Anything that has mass and takes up space
Element (92 naturally occurring elements)
A substance that cannot be broken down to other substances by chemical reactions. (92 naturally occurring elements)
Compound
A substance consisting of two or more different elements combined in a fixed ratio
Essential elements (20 - 25% of elements)
Elements that an organism needs to live a healthy life and reproduce. Humans require 25 elements
Trace elements
Elements required by an organism in only minute quantities. Iron (all forms of life) Iodine (thyroid gland)
96% of living matter
Just four elements—oxygen (O), carbon (C), hydrogen
(H), and nitrogen (N). COHN
Subatomic particles
Neutrons (neutral), protons (positive) and electrons (negative)
Atomic nucleus
The dense (positively charged) core at the center of an atom that contains neutrons and protons.
Dalton
A unit of mass a.k.a as amu (atomic mass unit). Protons and neutrons have masses close to 1 dalton. The mass of an electron is 1/2000 of a dalton.
Atomic number
The number of protons in an atom of a specific element. All atoms of a particular element have the same number of protons in their nuclei. Subscript to the left
Mass number
The sum of protons plus neutrons in the nucleus of an atom. Superscript to the left
Atomic mass
The total mass of an atom, close to its mass number (weighted average)
Isotopes
Different atoms of the same element that have different number of neutrons
Radioactive isotope
An isotope in which the nucleus decays spontaneously, giving off particles and energy which can transform the atom to an atom of a different element
Radioactive tracer
Radioactive isotopes that are incorporated into biologically active molecules, which are then used as tracers to track atoms during metabolism, the chemical processes of an organism
Half-life
The time it takes for 50% of the parent isotope to decay into its daughter isotope
Radiometric dating
Technique used to date materials by measuring the ratio of different isotopes present in the sample
Energy
The capacity to do work
Potential energy
The energy that matter possesses because of its location or structure
Valence electrons
The electrons in the outermost electron shell
Valence shell
The outermost electron shell
Noble gases
Gases that have completed valence shells. They are chemically inert
Electron shell
An orbit of electrons with a particular energy level and average distance from the nucleus
Chemical bond
An attraction between atoms that binds them together
Covalent bond
The sharing of a pair of valence electrons by two atoms
Molecule
Two or more atoms held together by covalent bonds
Single bond
One pair of shared electrons
Double bond
Two pairs of shared electrons
Valence
The bonding capacity of an atom which usually equals the number of unpaired electrons required to complete the valence shell
Electronegativity
The attraction of a particular atom for the electrons of a covalent bond
Polar covalent bond
A covalent bond whose electrons are not shared equally between the atoms giving each atom a partial charge
Ion
A charged atom or molecule that has gained or lost an electron
Cation
A positively charged atom or molecule
Anion
A negatively charged atom or molecule
Salt
Ionic compound. Compound formed by ionic bonds
Ionic bond
The attraction between two oppositely charged ions. An ionic bond can form when one atom transfers an electron to another atom
Weak bonds
Ionic bonds between ions dissociated in water, hydrogen bonds and van der Waals bonds. Weak bonds reinforce the three dimensional shape of large molecules (proteins)
Hydrogen bond
The attraction between an hydrogen atom and an electronegative atom
Van der Waals interactions
The charges that result in an atom by the random accumulation of electrons in one region
Chemical reaction
Involves the forming or breaking of a chemical bond
Reactant
A starting material in a chemical reaction
Product
The product of a chemical reaction
Chemical equilibrium
The forward and reverse reactions occur at the same rate. It is a dynamic equilibrium
