LO set 2 Flashcards
what types of atoms do covalent bonds form between
non-metal atoms
when is a covalent bond formed?
when two positive nuclei are held together by their common attraction for a
shared pair of electrons
what are the 7 elements that exist as diatomic molecules through the formation of covalent bonds?
H2, N2, F2, O2, I2, Cl2, Br2
what does the shape of simple covalent molecules depend on?
the number of bonds and the orientation of these bonds around the central atom
what 4 terms can be used to describe the shape of simple covalent molecules?
linear, angular, trigonal pyramidal or tetrahedral
what 2 structures can covalent substances form?
discrete molecular or giant network structures
what kind of bonds do covalent molecular substances have?
strong covalent bonds within the molecules and only weak attractions between the molecules
why do covalent molecular substances have low melting and boiling points?
only weak forces of attraction between the molecules are broken when a substance changes state
why don’t covalent molecular substances conduct electricity?
they do not have charged particles which are free to move
what kind of bonds do covalent network structures have?
strong covalent bonds within one giant structure
why do covalent network structures have very high melting and boiling points?
the network of strong covalent bonds is not
easily broken
why do covalent network substances not conduct electricity?
they do not have charged particles which are free to move.
when are ions formed?
when atoms lose or gain electrons to obtain the stable electron arrangement of a noble gas
why do metal atoms lose electrons?
to form positive ions
do non-metal atoms gain or lose electrons when forming negative ions
gain
what is an ionic bond?
the electrostatic attraction between positive and negative ions
what is the name of the structure ionic compounds form and how are they formed?
lattice structure. oppositely charged ions with each positive ion
surrounded by negative ions and each negative ion surrounded by positive ions
how are compounds named?
from the names of the elements from which they are formed.
how many elements do compounds that end in -ide contain?
only 2
how can chemical formulae be written for two element compounds?
using valency rules and a Periodic
Table.
how is the valency of a metal element indicted?
in roman numerals
what does the chemical formula of a covalent molecular substance indicate?
it gives the number of each type of atom present in a molecule
what does the formula of a covalent network give each type of atom in the substance?
the simplest ratio
what are ions that contain more than one type of atom often referred to as?
group ions
how many bonds can be formed between atoms and what does it lead to?
more than one atom. this leads to double and triple covalent bonds
how can covalent molecular substances, that are in soluble in water, be dissolved?
they may dissolve in other liquids
do covalent structures dissolve?
in general, no
are ionic compounds soluble in water?
not all but many are.
what happens when an ionic compound dissolves?
the lattice structure breaks up allowing water molecules to surround the separated
ions.
when do ionic compounds conduct electricity and why?
only when molten or in solution as the lattice structure breaks up allowing the ions to be free to move.
how can conduction in ionic compounds can be explained?
by the movement of ions towards oppositely
charged electrodes
how many elements do compounds that end in -ite or -ate contain?
2 elements and oxygen
what other way can chemical formula be determined?
from names with prefixes
how are charges and the no. of atoms/ions written?
charges must be superscript and numbers of atoms/ions must be subscript
