Unit 2 Flashcards
An atom’s reactivity is determined by its _____.
electron configuration
consists of two or more elements in a fixed ratio
compound
The hydrogen atoms of a water molecule are bonded to the oxygen atom by ________ bonds
Polar covalent
whereas neighboring water molecules are held together by ________ bonds.
hydrogen
A covalent bond is likely to be polar if _____.
one of the atoms sharing electrons is much more electronegative
Water can resist temperature change because _____.
heating water absorbs energy by disrupting the hydrogen bonds before evaporation can occur
A material that resists a change in pH is called a(n) _____.
Buffer
________ are weak bonds that are not strong enough to hold atoms together to form molecules but are strong enough to form bonds within and around large molecules.
hydrogen bonds
How do isotopes of an element differ?
by the atomic mass number
Typically, nitrogen atoms are composed of electrons, protons, and neutrons. An isotope of nitrogen could
have more neutrons than the usual nitrogen atom.
The number of _______ will equal the number of ________ in an electronically neutral atom.
electrons, protons
In a water molecule, hydrogen and oxygen are held together by a ________ bond.
polar covalent
The number of protons in an uncharged atom _____.
equals the total number of electrons in the orbital shells
Which trace element needed by humans is commonly added to table salt?
Iodine
Because the molecules of water are farther apart in ice than in liquid water, _____.
Ice is able to float
A radioactive isotope is an isotope that
decays
the breaking and forming of chemical bonds that leads to a change in the composition of matter.
chemical reaction
the type of bond that holds the two oxygen atoms together is a
nonpolar covalent bond
the type of bond that holds one of the hydrogen atoms to the oxygen atom is a
polar covalent
When you add acid to a solution, _____.
the hydrogen ion concentration increases and lowers the pH
- The term for a solution with a low pH number, such as lemon juice or vinegar, is
acidic
The term for a solution that has an equal concentration of H+ and OH- is
neutral
The term for a solution with a high pH number, such as ammonia or bleach, is
Basic
an acid is a compound that donates ______ to a solution.
H+
The higher the pH number, the higher the concentration of __________ in a solution.
OH-
A substance that accepts H+ when they are in excess and donates H+ when their concentration drops is called a(n)
buffer
For most atoms, a stable configuration of electrons is attained when the atom __________.
has a completely filled outermost shell
proton characteristics
charge +1, in the nucleus, determines atomic # and 1/2 determines atomic mass, is characteristic for each element
Neutrons characteristics
no charge, in the nucleus, 1/2 determines atomic mass, may differ in isotopes
electrons characteristics
charge is -1 and moves in an electron cloud.
Which four elements are the primary components of important biological molecules, such as proteins, fats, and carbohydrates?
CHON
carbon, hydrogen, oxygen, and Nitrogen
Water molecules stick to other water molecules because
hydrogen bonds form between the hydrogen atoms of one water molecule and the oxygen atoms of other water molecules.
what are the trace elements?
zinc, iodine: thyroide, fluoride:bad teeth , iron: anemic
Two atoms of the same element must have the same number of _____.
protons
Table salt is formed when
sodium donates its single outer electron to chlorine.
In some areas, fluoride is added during the municipal water treatment process in order to help
to prevent tooth decay
An ionic bond is shown below. It forms as a result of _____.
an attraction between atoms that have opposite charges
A polar covalent bond _____.
results in an unequal sharing of electrons
Sodium chloride (NaCl) dissolves in water because water molecules _____.
are polar
The partial charges in this water molecule occur because of _____.
the unequal sharing of electrons between hydrogen and oxygen
Which of the following best describes the atomic number of an atom?
the number of protons in the atom
Ionic bonds form when _____.
one atom transfers an electron to another atom
A substance that cannot be broken down into other substances by ordinary chemical procedures is known as a(n) _____.
element
The __________ of water molecules and the hydrogen bonds between water molecules explain most of water’s life-supporting properties.
polarity
The ___________of water molecules to each other helps transport water from the roots to the leaves in plants.
cohesion
When water warms or cools, ________ either break or form.
hydrogen bonds
Thus, water absorbs or releases a great deal of
_______, helping to moderate temperatures.
heat
Because ________is less dense than liquid water, it floats and protects lakes and oceans from freezing solid.
Ice
Water is a versatile _________
solvent
Blood and other biological fluids are aqueous solutions with a diversity of dissolved _________
solutes
