Chapter 2: chemistry Flashcards
An element is a substance that
cannot be broken down to other substances by chemical reactions
A compound is a substance
consisting of two or more elements in a fixed ratio
what elements make up 96% of living matter?
Carbon, hydrogen, oxygen, and nitrogen make up 96% of living matter
Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur
Atoms are composed of subatomic particles
Relevant subatomic particles include:
Protons (positive charge) Neutrons (no electrical charge) Electrons (negative charge)
Neutrons and protons form the
atomic nucleus
____ form a cloud around the nucleus
Electrons form a cloud around the nucleus
An element’s atomic number is
the number of protons in its nucleus
An element’s atomic mass number is
the sum of protons plus neutrons in the nucleus
___ are atoms of an element that differ in number of neutrons
Isotopes
____ decay spontaneously, giving off particles and energy
Radioactive Isotopes
Some applications of radioactive isotopes in biological research are:
Dating fossils
Tracing atoms through metabolic processes Diagnosing medical disorders
___ is the capacity to cause change
Energy
___ is the energy that matter has because of its location or structure
Potential energy
An electron’s state of potential energy is called its energy level, or ___
electron shell
___ are those in the outermost shell, or ___
Valence electrons, valence shell
The chemical behavior of an atom is mostly determined by the ___
valence electrons
Elements with a full valence shell are ___
chemically inert
Atoms with incomplete valence shells can…
share or transfer valence electrons with certain other atoms
atoms staying close together, held by attractions called ___
chemical bonds
A ___ is the sharing of a pair of valence electrons by two atoms
covalent bond
In a covalent bond, the shared electrons count as part of each atom’s valence shell
(example 2 Hydrogen atoms. both have 1 electron in the first shell. H2 would let them share their electrons completing their first shell with now 2 electrons)
A ___ consists of two or more atoms held together by covalent bonds
molecule
A single covalent bond, or ___, is the sharing of one pair of valence electrons
single bond
A double covalent bond, or ___, is the sharing of two pairs of valence electrons
double bond
The notation used to represent atoms and bonding is called a ___
For example, H–H
structural formula
a ___
For example, H2
molecular formula
A compound is a combination of two or more ___ elements
different
In a ___ covalent bond, the atoms share the electron equally
nonpolar
In a ___ covalent bond, the atoms do not share the electron equally
polar
Atoms sometimes strip electrons from their bonding partners
An example is the transfer of an electron from sodium to chlorine
ion
A ___ is a positively charged ion
cation
An ___ is a negatively charged ion
anion
An ___ is an attraction between an anion and a cation
ionic bond
Compounds formed by ionic bonds are called
___, or salts
ionic compounds
A __ forms when a hydrogen atom covalently bonds to one electronegative atom and is also attracted to another electronegative atom
hydrogen bond
(for instance a single hydrogen atom that’s bonded with an oxygen atom (let’s say H20) attracts a negatively charged oxygen atom from another H20 molecule)
___ interactions are weak attractions between molecules that are close together.
Van der Waals
A ___ is usually very important to its function
molecule’s shape
Biological molecules recognize and interact with each other with a specificity based on molecular shape Molecules with similar shapes can have similar biological effects
___ are the making and breaking of chemical bonds
Chemical reactions
The starting molecules of a chemical reaction are called ___
reactants
The final molecules of a chemical reaction are called ___
products
The number of atoms on the reactant side MUST BE ___ to the number of atoms on the product side.
EQUAL
The tendency of an atom to pull electrons toward itself is referred to as its
electronegativity
