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.