Science Lesson 3.3-3.4

a metal is made up of

positive metal ions with enough valence electrons "swimming" around to hold the ions together

covalent bond

this is the type of bond where electrons are shared between atoms Ex: H2O— electrons are shared between H's and O

nonmetals bond with nonmetals

covalent bond

water molecule

covalent bond

the four valence electrons of a carbon atom are in its

outermost energy level

in metallic bonding, there is a

"sea" or "cloud" of electrons

Bohr Model

shows the electrons but is not completely accurate (does not show the true arrangement of the electrons)

an atom of sulfur has

six valence electrons

valence electron

the electrons found in the outermost shell of an atom; this is where the chemical reactions and bonding takes place

the limited number of letters in the alphabet can be used to make many words, so

the elements combine to make many compounds

chemical changes change

the identity of substances

valence shell

the outermost shell of an atom

oxidation number

the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom

atoms are not created or destroyed by the chemical change

there were the same number and types of atoms before and after the chemical change

metalloids

these touch the staircase in the periodic table and have properties of both metals and nonmetals

best choice to show how atoms are arranged in molecules

Space Filling Model

when chlorine joins with sodium

chlorine gains one electron from sodium and becomes 1-

there are a few atoms in water

compared to the large amount of atoms in DNA

covalent compounds

compounds formed when covalent bonds occur

ionic compound

compounds formed when ionic bonds occur

Space-Filling Model

does not show characteristics of the atoms but shows their connections

if atom loses at least one electron

it will now have fewer electrons than protons; this results in overall positive charge

metallic bond forms between

metal atoms when their outermost energy levels overlap

metals bond with metals

metallic bond

80% of elements

are metals

covalent bond forms when

two nonmetal atoms atoms share one or more pairs of electrons

ionic bond

type of bond where atoms give electrons to other atoms and there is an attraction between oppositely-charged ions

an atom tends to form bonds

when its outermost energy level is not full

atoms are reactive

when their outermost energy levels are not full

when atoms are rearranged

chemical bonds have to be formed or broken

hydrogen

1 valence electron

sodium

1 valence electron

steps with metallic bonds to turn on a lamp

1. When you turn on a lamp, electrons move through the copper wire that connects the light bulb in the lamp to the electrical outlet. 2. The electrons that move are the valence electrons in the copper atoms. These electrons are free to move because the electrons are not connected to any one atom.

helium

2 valence electrons

carbon

4 valence electrons

chlorine

7 valence electrons

neon

8 valence electrons

H2+Cl2

=2HCl

chlorine atom fills its outermost energy level

Chlorine atom has seven valence electrons. It needs one more electron to have a full outermost energy level. Chlorine atom can gain an electron from a sodium atom. When this happens, chlorine atom becomes a negative ion (anion). The sodium atom that loses the electron becomes a positive ion (cation). The ions formed by both sodium and chlorine have eight valence electrons. Their outermost energy levels are now full. The negative and positive ions are held together by bonds. The result is sodium chloride (table salt).

using the periodic table to find valence electrons

Each family (column) of elements (excluding families 3-12) has a set number of valence electrons to its atoms. The first family has one valence electron. The second family has two, the thirteenth family has three, the fourteenth family has four, and so on.

not all of an atom's electrons

can interact with the electrons of other atoms to form bonds

fall leaves

The color of fall leaves is the result of a chemical change. Green pigments (chlorophyll) break down, but red and yellow pigments don't break down as easily. The green pigment's atoms are rearranged to become clear.

Bohr Model and valence electrons

The valence electrons are the electrons on the outer ost "layer" of the atom. The Bohr Model shows the number of valence electrons of each atom.

lithium, sodium, and potassium atoms are almost never found alone in nature

They are very reactive and form chemical bonds with other atoms. They are reactive because they only have one valence electron.

ion

a charged particle that forms when an atom loses or gains an electron

molecule

a group of atoms that are held together by chemical bonds

when two nonmetal atoms bond

a large amount of energy is needed for either atom to lose an ELECTRON, so, instead, they share so both will have filled outermost energy level

ion

a particle with a positive or negative charge

ion forms when

an atom gains or loses electrons from its outer, or valence, shell

chemical bond

an interaction that holds atoms or ions together

octet rule

atoms tend to gain, lose, or share electrons so as to have eight valence electrons

anion

atoms that gain electrons and have a negative charge

cation

atoms that lose electrons and have a positive charge "paws"

a chemical bond joins

atoms together in a water molecule

ionic bond forms when

atoms transfer one or more electrons to another to form a bond (brings oppositely charged ions together)

octet rule

atoms want to have 8 electrons in their outer shell to be stable

ions

atoms with either a positive or negative electrical charge

bonds are important for atoms

because forming bonds allows atoms to fill their outermost energy level (valence shell)

metals can be shaped

because of the nature of the bonds that form between metal atoms

during a chemical change

bonds break, and new bonds form

an atom can form bonds with other atoms

by gaining, losing, or sharing electrons

these atoms form bonds

by gaining, losing, or sharing valence electrons to form bonds

H2O bond

covalent bond in which two hydrogen atoms share their electrons with one oxygen atom; oxygen keeps most of the electrons, so it is negative; the hydrogens don't have many electrons, so they are positive

physical properties of ionic compounds

crystal lattice structure (think salt); crystals are hard and brittle— will break before they bend (hammer); poor conductors of electric current due to ions held tightly in place (if it melts, it becomes a better conductor); soluble in water (dissolves)

number of protons

does not change

the nucleus of an atom

does not change when an atom undergoes a chemical reaction

atoms are rearranged

during a chemical change when bonds break and form

best choice to show the locations of the parts of a sodium atom

electron cloud model; it shows the region where the electrons are found and the locations of the other parts of the atom

nitrogen atoms have

five valence electrons

ductile, ductility, etc.

formed into thin wires

(ionic bond) electrons are tranferred

from a metal (+) to a nonmetal (-)

(ionic bond) valence electrons move

from outer shell of the metal atom to the outer shell of the nonmetal atom

oxygen would like to

gain 2 electrons

nitrogen would like to

gain 3 electrons

carbon would like to

gain 4 electrons

properties of metallic bonds

good electrical conductors due to electrons moving freely; malleable and ductile due to free-moving electrons

malleable

hammered into sheets

metallic bonds

have metal ions and free electrons from outer shells of metal atoms

first electron shell can

hold 2 electrons

outermost electron shell can

hold 8 electrons

Which atoms are likely to form chemical bonds with other atoms?

hydrogen, sodium—> lose their one valence electron chlorine—>has 7 valence electron, wants to gain one carbon—> gain or lose 4 valence electrons They all don't have a full valence shell

atoms will be neutral

if there is an equal number of electrons and protons

nonmetals bond with metals

ionic bond

sodium chloride molecule

ionic bond

if atom gains at least one electron

it will now have more electrons that protons; this results in overall negative charge

nitrogen atoms are

likely to form bonds with other atoms because they do not have full valence shells

physical properties of covalent compounds

low solubility in water (some do, some don't) Ex: wax doesn't dissolve in water; low melting and boiling points— covalent bonds don't break as easily as ionic bonds do; poor electrical conductivity— most are unable to conduct electricity

copper metal is held together by

metallic bonding, in which electrons flow around copper ions

metallic bonds are

responsible for the properties of metals

Electron Cloud Model

shows the locations of the parts of the atom but does not show individual electrons

when sodium joins with chlorine

sodium loses one electron to chlorine and becomes 1+

chemical changes don't change

the number of atoms (don't create or destroy atoms)

how many of each type of atoms are there before and after a chemical change

the same amount

metals

these are found to the left of the staircase and form ionic bonds with nonmetals: give away electron(s) and become positive (hydrogen is the exception)

nonmetals

these are found to the right of the staircase and form covalent bonds with each other, or take electrons away from metals to form ionic bonds and become negative

hydrogen and oxygen of H2O are bonded

where each hydrogen touches the oxygen

The Bohr model of a neon atom (versus that of a nitrogen atom)

would have 10 electrons and 8 valence electrons instead of 7 electrons and 5 valence electrons