Ch. 2 Flashcards
Electrons charge
Negative
What are the properties of an atom?
Electrons, protons, neutrons
Protons charge
Positive
Neutrons charge
Neutral
Atomic number
The number of protons in the nucleus that defines the element
The Atomic mass
The number of protons plus the number of neutrons
Isotopes
Forms of an element that have the same number of protons but differ in the number of neutrons their atoms carry
Isotopes are atoms of an element that differ in _____
Mass number
Atoms of ______ spontaneously emit subatomic particles or energy
Radioisotopes
Radioactive decay
The process by which atoms of a radioisotope emit energy and/ or subatomic particles when their nucleus spontaneously decays
Radioisotope
Isotope with an unstable nucleus
Researchers use radio scopes to make ____ that track biological processes inside living organisms
Tracers
Why do electrons matter to atoms ?
- they share and donate then
- whether atoms interact with other atoms depends on how many electrons they have
What are Shell models?
Help us visualize how electrons arranged around the atoms nucleus from the innermost shell outward
What is an ion?
The charge an atom with a different number of electrons and protons
Electronegativity
A measure of how strongly an atoms attracts electrons from other atoms
A ______ is an attractive force that unites two atoms as a ______ when their electrons interact.
Chemical bond, molecule
Compound
A molecule that consists of two or more elements, productions of elements do not vary
Mixture
An intermingling of substances, the proportions of the substances can vary because chemical bonds do not form
The three types of chemical bonds:
- Ionic bonds
- Covalent bonds
- Hydrogen bonds
Ionic bond
A strong association between oppositely charged ions that arises from mutual attraction of opposite charges
A _____ bond is formed when two ions are held together by the attraction of opposite electrical charges.
Ionic
Covalent bond
Chemical bond in which two atoms share a pair of electrons
Polarity
Any separation of charge into distinct positive and negative regions
Hydrogen bond
Attraction that forms between a covalently bonded hydrogen atom and another atom taking part in a separate covalent bond
_____ can form hydrogen bonds, non-polar molecules cannot.
Polar molecules
Form between opposite charges in polar water molecules
Hydrogen bonds
Water is essential to life because of its unique properties:
- solvent for salts and other polar solutes
- resists temperature changes
- cohesion
Water is a ______ that easily dissolves salts, sugars, and other polar substances
Solvent
Solvent
Liquid that can dissolve other substances
Solute
A dissolved substance
A compound that dissolves easily in water and releases ions
Salt
Hydrophilic
Substance that dissolves easily in water
Hydrophobic
Substance that resists dissolving in water such as oil. Usually non-polar molecules
What is cohesion?
- Tendency of molecule to stick together
- pulls water upward in plants
- causes surface tension
Cohesion of water molecules resists _____
Evaporation
_____ stability is important for homeostasis; most molecules of life function within a certain temperature range
Temperature
Temperature
Measure of molecular motion
What is pH?
Measure of concentration of hydrogen ions in a fluid
Concentration
Number of molecules or ions of a solute per unit volume of a solution
Acid
Substance that releases hydrogen ions in water, the higher the number of ions , the lower the pH
Base
Substance that accepts hydrogen ions in water
Buffer
Keeps a solution within a consistent range of pH
How does a buffer maintain as consistent pH?
Alternately donating and accepting ions that contribute to pH