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48 Cards in this Set

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anything that takes up space and has mass.


substances that cannot be chemically broken down to other types of matter.


made up of two or more elements combined in a fixed ratio.

96% Elements of Life

Carbon, Oxygen, Hydrogen, and Nitrogen.

trace elements

like Iron (Fe) and Iodine (I) may be required in very minute quantities.

The remaining 4% of The Elements of Life

Calcium (Ca), Phosforus (P), Potassium (K) , Sulfur (S), Sodium (Na), Chlorine (Cl), and Magnesium (Mg)


the smallest unit of matter retaining the properties of a particular element.


uncharged subatomic particles found in the nucleus.


positively charged subatomic particles packed tightly together to form the atomic nucleus.


negatively charged subatomic particles that form a cloud around the atomic nucleus.

a dalton

is the measurement unit for atomic mass. Protons and neutrons have a similar mass of about 1.7 x 10^-24 grams or close to one dalton each. Electrons have negligible mass.

atomic number

characteristic to each element, is the number of protons in the nucleus of each of its atoms.

mass number

equal to the number of protons and neutrons in the nucleus and approximates the mass of an atom of that element in daltons.

atomic mass

the total mass of an atom.


number of neutrons vary among the atoms of an element, with the number of protons constant. slightly different masses but the same chemical behavior.

radioactive isotopes

unstable isotopes. spontaneously decaying, giving off particles and energy. important tools in research and medicine. too much exposure poses a significant health hazard.


the capacity to cause change.

potential energy

energy stored in matter as a consequence of its positon or structure.

electron shells

electrons can be located in different shells surrounding the nucleus and increase in potential energy as their distance from the positively charged nucleus increases.

valence electrons

electrons in its outermost electron shell that dictates the chemical behavior of an atom by their distribution.

valence shell

outermost electron shell


is the three dimensional space or volume within which an electron is most likely to be found. No more than two electrons can occupy the same orbital.

chemical bonds

hold atoms together that have incomplete valence shells by either sharing or transferring electrons such that each atom is able to complete its valence shell.

covalent bond

when two atoms share a pair of valence electrons.


consists of two or more atoms held together by covalent bonds.

structural formula

indicates both the atoms and bonds in a molecule.

a molecular formula

indicates only the kinds and numbers of atoms.

The _________ or bonding capacity of an atom usually equals the number of unpaired electrons in its valence shell.


What are the valences of the four most common elements of living matter?



the attraction of a particular atom for shared electrons.

If the atoms in a molecule have similar electronegativities, the electrons remain ______________ and the bond is said to be a _________________.

equally shared and nonpolar covalent bond.

If one is more electronegative, it does what and forms what

pulls the shared electrons closer to itself creating a polar covalent bond.


charged atoms

ionic bonds

if two atoms are very different in their attraction for valence electrons, the more electronegative atom may completely transfer an electron from the other atom, resulting in the formation of charged atoms.


ion that lost the electron is positively charged.


atom that gained the electron.

ionic bond

may hold these ions together because of their opposing charges.

ionic compounds

salts, often exists as three dimensional crystalline lattice arrangements held together by electrical attractions.

hydrogen bonds

hydrogen bond that is covalently bonded to an electronegative atom has a partial positive charge and can be attracted to another nearby electronegative atom.

van der Waals interactions

all atoms and molecules are attracted to each other when in close contact by these. Momentary uneven electron distributions produce changing positive and negative regions that create these weak attractions.

chemical reactions

involve the making or breaking of chemical bonds.

chemical equilibrium

reached when the forward and reverse reactions proceed at the same rate, and the relative concentrations no longer change.

Word Roots: an-

not (anion: negatively charged ion)

Word Root: co-


Word Root: -valent

strength (covalent bond: a strong bond between atoms that share one or more pairs of valence electrons)

Word Root: electro-

electricity (electronegativity: the attraction of a given atom for the electrons of a covalent bond)

Word Root: iso-

equal (isotope: one of several forms of an element, each with same number of protons but a different number of neutrons)

Word Root: neutr-