chapter 4
chemical formula
symbols that shows the ratio of elements in a compound
What is special about the halogens?
(Group 17) They easily react with other elements because they only need to gain one electron as they have 7 valence electrons
how are the formulas and names of ionic compounds written?
- Formulas: for an ionic compound, write the symbol of the positive ion and then the symbol of the negative ion. add the subscripts that are needed to balance the charges - Names: for an ionic compound, the name of the positive ion comes first, followed by the name of the negative ion
what are the properties of ionic compounds?
- form hard brittle crystals that have high melting points - conduct electric current when dissolved in water or melted
8 valence electrons
Makes an element stable and nonreactive
molecule
a molecule is a neutral group of atoms joined by covalent bonds
subscript
a number that is written below and behind the chemical symbols in a chemical formula.
electron dot diagram
shows the chemical symbol with dots surrounding it to represent the valence electrons of that atom
What are the properties of metals?
(again) shiny luster, high levels of malleability, ductility, electrical conductivity and thermal conductivity
an electron dot diagram shows what?
- how many valence electrons an atom has - the elements on the outside ring only - the valence electrons on the valence ring
how do ions form?
- when an atom loses a valence electron, it loses a negative charge. it becomes a positive ion. - when an atom gains an electron, it gains a negative charge and becomes a negative ion
Why is hydrogen all alone on the periodic table?
1- it is a nonmetal on the metal side of the table 2- has very different properties than the alkali metals. 3- Hydrogen always shares its electron when forming compounds with other nonmetals to obtain a stable arrangement of 2 electrons.
double bond
2 atoms share 2 pairs of electrons
Metallic Bond
A bond formed by the attraction between positively charged metal ions and the electrons around them.
How are elements in a group related regarding their valence electrons?
Except for period 1, elements in a group always have the same number of valence electrons. This gives them similar properties
polyatomic ion
Ions that are made of more than one (1) atom, can have an overall positive or negative charge
What is the structure of a metal crystal?
It is composed of closely packed, positively charged metal ions. The valence electrons drift among the ions.
Alloy
Mixture made of two or more elements, at least one of which is a metal.
crystal
The ions form an orderly, three-dimensional arrangement.
How do metalloids bond?
They can lose or share electrons when they combine with other elements
single bond
a chemical bond in which one pair of electrons is shared between 2 atoms.
molecular compound
a compound that is made up of molecules
nonpolar bond
a covalent bond when electrons are shared equally
polar bond
a covalent bond when the electrons are shared unequally
ion
an atom or group of atoms that has an electric charge
why are metallic bonds good conductors or heat and electricity
because their not chemical bonds, an their valence electrons are allowed to move freely around their ring so they have more space. for heat, the more energy the electrons have, the warmer the atom gets and by being able to move around that should cause a lot of energy
why do the noble gasses not react with other elements
because their valence ring is filled with electrons and no space for more electrons
- the number of valence electrons in each atom helps determine the ---- of that element
chemical properties
valence electrons
electrons that have the highest energy, they determine the chemical properties of its element
What determines the reactivity of metals?
how easily the atom loses it's valence electrons
How does the reactivity of metals change as you move from left to right on the periodic table?
it decresses
What determines an element's chemistry?
its amount of valence electrons
ionic compound
made up of an equal amount of positive and negative ions
What do nonmetals usually combine with, and how?
metals, by gaining electrons
example of polar and example of non polar and why are they that
non polar: the bond of 2 hydrogen atoms because they equally share their pair of electrons to form a molecule - polar bond: water, h2o, oxygen spends more time with the electrons then the 2 hydrogen atoms do
draw and label a sodium and chlorine atom before and after bonding to each other complete with dot diagram and charges
paper
diff between polar bonding and non polar bonding
polar: -uneven sharing of electrons -element with higher atomic # -has more attraction nonpolar: -equal atomic # -share = electrons -diatomic (same element)
- when a neutral atom loses a valence electron, it loses a negative charge. It becomes a ---- ion - when a neutral atom gains an electron, it gains a negative charge and it becomes a ---- ion.
positive negative
ionic bond
the attraction between two oppositely charged ions
how are atoms held together in a covenant bond?
the attractions between the shared electrons and the protons in the nucleus of each atom hold them together.
covalent bond
the chemical bond formed when 2 atoms share electrons
chemical bond
the force of attraction that holds atoms together as a result of the rearrangement of electrons between them. (energy is stored here)
How can nonmetals become stable?
they can gain or share valence electrons to have a full valence ring
How do metals chemically react?
they lose their valence electrons
why do atoms bond
they want to be more stable by filling up their valence ring with valence electrons
how do bonded atoms become partially charged
unequal sharing of electrons causes covalently bonded atoms to have slight electric charges
what are properties of molecular compounds
unlike ionic compounds, molecular compounds usually do not conduct electric current when melted or dissolved in water. - also compared to ionic compounds, molecular compounds generally have lower melting and boiling points
triple bond
when two atoms share 3 pairs of electrons
Can nonmetals combine with anything other than metals, and if so, how?
yes, other nonmetals or metalloids by sharing electrons