Campbell Biology Chap 2 Flashcards
What is an element
Substance that cannot be broken down to other substances by chemical reactions
What is a compound
Substance Consisting of 2 or more different elements combined in a fixed ratio
What is a Dalton
Essentially the same thing as an atomic mass unit(or AMU)
What is an Isotope
Atoms with more neutrons than those of the same atoms
What is a Radioactive Isotope
one in which the nucleus decays spontaneously, giving off particles and energy
When the radioactive decay leads to a change in the
number of ____
Protons, Leading to the element to change into a different one
A “parent” isotope decays into its “daughter” isotope at a
fixed rate, expressed as the ________ of the Isotope
Half-Life
What is Radiometric Dating
Scientists measure the ratio of different isotopes and calculate how many half-lives (in years) have passed since an organism was
fossilized or a rock was formed
Atoms are mostly
Empty Space
_______ is the energy that matter possesses because of its location or structure
Potential Energy
Matter has a natural tendency to move toward the ____
possible state of potential energy
Lowest
Describe Electron shell
regions surrounding the atomic nucleus containing a specific number of electrons
As electrons get farther away from the nucleus, how does the potential energy change
Increasing Potential Energy
When an electron loses energy what happens
Moves to a lower shell
When an electron gains energy what happens
Moves to higher shell
What are valence electrons
number of electrons in its outermost shell
Atoms with the same number of electrons in their valence shells do what
Exhibit similar behaviour
Elements with a full valence shell are
Un-reactive
What is the atomic mass of an element that has isotopes
average of their masses
Describe covalent bonds
sharing of a pair of valence electrons by two atoms
Strongest type of chemical bonds
Covalent Bonds
First shell has a maximum of how many electrons
2
Second shell has a maximum of how many electrons
8
third shell has a maximum of how many electrons
18
Formula for calculating maximum number of electrons in a given shell number
2n^2
What is Electronegativity
the tendency of an atom participating in a covalent bond to attract the bonding electrons
nonpolar covalent bond
When the Compound has elements of similar electronegativity
polar covalent bond
When the compound has elements of different electronegativity
What is an Ionic Bond
when two atoms are so unequal in their attraction for valence electrons that one of the atoms strips an electron from the other atom, which causes them to attract each other due to the formation of 2 ions of opposite charge
positively Charged ion
Cation
Negatively charged ion
Anion
Compounds formed by Ionic bonding are also called
Salts
Ionic compounds are not considered
Molecules
Why do Hydrogen Bonds form
When a hydrogen atom is covalently bonded to an electronegative atom, the hydrogen atom has a partial positive charge that
allows it to be attracted to a different electronegative atom with
a partial negative charge nearby
What are van der waal’s interactions
Nonpolar Covalent bonds exhibit unevenly distributed electrons, resulting in everchanging regions of positive and negative charge that enable all atoms and molecules to stick to one another
