Biology Chapter 2
An________ is a type of bond that joins atoms.
ionic bond
A(n) ________ can be defined as a substance that prevents the pH of a solution from changing by either releasing or absorbing H+ in a solution.
buffer
Chemicals or a combination of chemicals that keeps pH levels within normal limits are called _______.
buffers
The number of neutrons present in the nucleus of an average atom of any given element is best estimated by
subtracting the number of protons from the mass number.
4 elements that makes up most living organisms
Nitrogen Oxygen, Carbon, and Hydrogen
Which one of the following is the smallest unit of matter that has all the properties of an element?
atom
During an ________, atoms give up or receive electrons to ensure a stable outer shell.
ionic reaction
Atoms of the same element with varying numbers of neutrons, some of which produce radiation that may be useful medically, are called ________.
isotopes
Iron is not one of the most common elements in ________?
living things
Anything that takes up space
matter
A single atom may form bonds with more than one other atom, like ________, which is a carbon atom bound to four hydrogen atoms.
methane
The ________ displays all of the elements, and therefore the atoms, based on their chemical and physical properties.
periodic table
The ________ is written below the atomic symbol and reflects the number of protons and neutrons in an atom.
atomic mass
The ________ is written above the atomic symbol and reflects the number of protons the atom has and makes it unique.
atomic number
The ________ states that elements consist of tiny particles called atoms.
atomic theory
In the human body, pH needs to be kept within a narrow range in order to maintain ________.
homeostasis
These chemicals work by taking up excess________ when acids are added to the body and ________ when bases are added to the body.
hydrogen ions; hydroxide ions
Sometimes, atoms share more than two electrons to complete their ________and will share two pairs to create a________or three pairs to create a ________.
octets; double bond;triple bond
For example, two hydrogen atoms will share their electrons and these electrons will spend part of their time in the ________shell of each atom.
outer
Atoms with more than one shell are most stable when the________contains 8 electrons.
outer shell
3 states of matter
solid, liquid, gas
Why do cells need buffering agents?
to minimize the changes in pH of their internal environment
An element has an atomic number of 78. The number of protons and electrons in a neutral atom of the element are
78 protons and 78 electrons.
O2 is not a ________?
compound
the two types of bonds that are involved in compound formation
Ionic and Convalent Bonding
In covalent bonding, the atom will ________the electron leaving both atoms with an outer shell of 8 electrons,
accept
Diseases such as diabetes and congestive heart failure may bring on a condition called _________, in which the body is unable to buffer the excessive production of hydrogen ions.
acidosis
The number and arrangement of electrons in an atom governs its
chemical activity.
The pH scale is a mathematical indicator of the
concentration of H+ present in a solution.
An atom's valence electron shell
determines its chemical reactivity.
A(n) covalent bond results when two atoms share ________in order to have a completed outer shell.
electrons
A covalent bond occurs when
electrons are shared between two atoms to complete their octets.
Nonliving and living matter are composed of ________that cannot be broken down further.
elements
In the formation of the compound NaCl, sodium will ________ one of its outer shell electrons.
give up
An atom that has an electrical charge is called a(n)
ion
