Biology Concepts and Applications Chapter 2
Why Electrons Matter
How an atom interacts with other atoms depends on the number and arrangement of its electrons
The Power of Hydrogen
Most of the chemistry of life occurs in a narrow range of pH, so the fluids inside organisms are buffered to stay within that range
Elements
a substance that consists only of atoms with the same number of protons.
chemical bond
an attractive force that arises between two atoms then electrons interact.
polarity
any separation of charge into distinctive positive and negative regions.
ion
atom that carries a charge due to an unequal number of protons and electrons
molecule
atoms of the same of different elements joined by chemical bonds.
hydrogen bond
attraction that forms between a covalently bonded hydrogen atom and electronegative atom taking part in another covalent bond.
covalent bond
chemical bond in which two atoms share a pair of electrons.
sphere of hydration
clustering of water molecules around a solute.
salt
compound that dissolves easily in water and releases ions other than H+ and OH-
hydrophillic
dissolves easily in water
Atoms
particle that is a fundamental building block of matter consists of varying numbers of protons, electrons, and neutrons.
protons
positively charged subatomic particle in the nucleus of all atoms.
hydrophobic
resists dissolving in water.
buffer system
set of chemicals that can counter pH shifts in a solution by donating or accepting H+ or OH-
ionic bond
strong mutual attraction of two oppositely charged ions
solvent
substance that dissolves other substances.
solute
substance that is being dissolved.
bases
substances that accept hydrogen ions.
acids
substances that release hydrogen ions in water
periodic table of elements
tabular arrangements of the elements by atomic number
adhesion
tendency of molecules to resist from sticking together.
cohesion
tendency of molecules to stick together
evaporation
transition of a liquid into a gas, which requires energy input.
mixture
two or more types of molecules intermingling in proportions that vary because substances do not bond with each other.
compounds
type of molecule that has atoms of more than one element.
Atoms Bond
- Atoms of many elements interact by acquiring, sharing, and giving up electrons - Interacting atoms may form ionic, covalent, or hydrogen bonds
Water of Life
- Water stabilizes temperature, has cohesion, and can act as a solvent for many other substances - These properties make life possible
Atoms and Elements
Atoms, the building blocks of all matter, differ in their numbers of protons, neutrons, and electrons
radioisotopes
isotope with an unstable nucleus; decays into predictable daughter elements at a predictable rate.
electronegativity
measure of an atom's ability to pull electrons away from other atoms.
temperature
measure of molecular motion.
pH scale
measure of the acidity of a solution.
shell model
model for how electrons are distributed in an atom
tracer
molecule with a detectable label attached; researchers can track it after delivering into a cell.
Electrons
negatively charged subatomic particles that occupy orbitals around the atomic mass.
atomic number
number of protons in the nucleus of atoms of a given element.
isotopes
one form of an element that differ in the number of neutrons.
