Science- Valence Electrons/Bonds (for test 5/16-8th Grade)

What is a molecule?

A covalent compound is called a molecule A molecule is when a neutral group of atoms is joined by covalent bonds More than 1 nonmetal atom held together by chemical bonds

What is a metallic bond? Describe metallic bonds.

A metallic bond is a bond formed between metal atoms that share their pooled valence electrons Since metals want to lose their electrons they become positive ions and a "sea of a electrons" surrounds them

What does am element's place on the periodic table (its family/group) tell you about that element?

It tells you the number of valence electrons it has

How do you name molecules?

Less electronegative (Closer to metals/left, lower down) go first and the more electronegative go second 2. The ending is -ide 3. Prefixes are used (except the first element doesn't get mono) based on the subscript numbers

What is an alloy?

Metallic compounds are metals or metal alloys. (metal mixtures), like mixing copper and zinc

Do ionic compounds have charges?

NO

What is a nonpolar bond?

Nonpolar bonds Equal sharing Nonpolar bond - flourine molecule (equal pull) Polar bond - Hydrogen flourine molecule (unequal pull)

Are metals generally givers or takes of electrons?

metals are givers of electrons

Are nonmetals generally givers or takes of electrons?

nonmetals are takers of electrons

What do we call ions that are made of more than one atom?

polyatomic ions

Where do you see the charge of the compound?

top right corner

What is an ionic bond? How does an ionic bond form?

-Ionic bonds form between metals (givers of electrons) and nonmetals (takers of electrons) -ionic bonds are a result of the attraction between positive and negative ions. Oppositely charged ions

What are the prefixes? Need to know what number they represent. Practice naming

1- mono 2-di 3- tri 4- tetra 5-petra 6-hexa 7- hepta 8- octa

What is a chemical bond?

A chemical bond is the force of attraction that holds 2 atoms together as a result of the rearrangement of electrons between them. Chemical bonds can result from sharing electrons or transferring electrons

Describe multiple bonds: what is a single bond? double bond? triple bond?

A single bond is when 2 atoms share 1 pair of electrons ( 2e-) A double bond is when 2 atoms share 2 pairs of electrons (4e-) A triple bond is when 2 atoms share 3 pairs of electrons ( 6e -)

What is an ion?

Ions are atoms that have lost or gained electrons and they have an electric charge (either positive if they lost electrons or negative if they gained electrons)

What makes an atom stable?

Atoms of most elements are more stable (less likely to react) when they have a full outer shell or have 8 valence electrons (or 2 for hydrogen and helium)

What does it mean when we say that there can be UNEQUAL sharing of electrons?

Atoms of some elements pull more strongly on shared electrons than do atoms of other elements As a result the electrons are pulled more toward one atom causing the bonded atoms to have slight electrical charges The charges are not as strong as ionic charges

why do atoms react? What is the goal?

Atoms usually react in a way that makes them more stable Valence electrons are either gained, shared, or lost so that they have 8 valence electrons.

What is a covalent bond?

Covalent bonds form between NONMETALS Covalent bonds are formed when 2 atoms SHARE electrons Most nonmetals can even bond with another atom of the same element

How many valence electrons can each element have?

Each element has a specific number of valence electrons ranging from 1 to 8

What is electronegativity?

Electronegativity is how strong a pull there is on the electrons: consider:how many shells there are and how many electrons are in the outermost shell

Describe why atoms can form more than one covalent bond. Explain why nonmetals form covalent bonds instead of ionic bonds like metals do.

Except for hydrogen, the number of covalent bonds that nonmetals atoms can form equals the number of electrons needed to make a total of 8 Only nonmetals form covalent bonds, anything that has less than 3 will get rid of them not share 14 - 4 bonds 15 - 3 bonds 16 - 2 bonds 17 - 1 bond

What does and atom needs to to be stable? What does an atom do to become as stable as they can?

For an atom to be stable needs to have same number of protons and electrons and a full valence shell Atoms try to get as stable as they can, so they bond with atoms to be closer to being stable

What is an electron dot diagram?

In an electron dot diagram, each valence electron is drawn as 1 dot surrounding the chemical symbol for the element. Only the outermost (valence) electrons are drawn in a dot diagram

What make up ionic Compounds?

Ionic Compounds are compounds that consist of positive and negative ions. When ionic compounds form, the ions come together in a way that balances out the charges on the ions The chemical formula reflects this balance All ions have a charge What they form is neutral and stable Metals become + ions Non metals become - ions All the charges are balanced (if it's Neutral)

Which is stronger: ionic or covalent bonds?

Ionic bonds are stronger because they don't have to share.

What is a polar bond? describe it

Polar bonds Unequal sharing Stronger pull is slightly negative Weaker pull is slightly posotive

What are the two types of covalent bonds?

Polar bonds and nonpolar bonds

Which is stronger: polar or nonpolar bonds and why?

Polar bonds are stronger than nonpolar bonds. This makes polar molecules stronger.

Do polar/nonpolar bonds mix well?

Polar molecules mix well with other polar molecules but not with nonpolar molecules. (Ionic and polar will mix together) (nonpolar will stay with nonpolar)

What are polyatomic ions?

Polyatomic ions are ions that are made of more than one atom -once they bond, they tend to stay together -we put them in brackets to show they are together

Naming Ionic Compounds

Positive Ion (1st) negative Ion (2nd) The ending is -ide unless you have a polyatomic negative ion (those endings don't change)NH4NO3 Ammonium Nitrate

What does an atom's reactivity depend on? (Why are some atoms more reactive than other atoms?)

Reactivity depends on how easily an element gains or loses its valence electrons- meaning it depends on the number of valance electrons an atom has Noble gases do not react easily with other elements because they usually have 8 valence electrons (their outer shell is full so it is stable and non-reactive) Group 1 (alkali metals) and Group 17 (halogens) are most reactive because they only have to lose or gain 1 electron to become stable (they are 1 electron away from having a full outer electron shell)

Write the Formula for Each Compound: You can practice more on your own if you want to Sodium (Na) Bromide (Br) Lithium (Li) Oxide (O) Magnesium (Mg) Sulfide (S) Aluminum (Al) Fluoride (F) Potassium (K) Nitrate (NO3)

Sodium (Na) Bromide (Br) NaBr Lithium (Li) Oxide (O) Li2O Magnesium (Mg) Sulfide (S) MgS Aluminum (Al) Fluoride (F) AlF3 Potassium (K) Nitrate (NO3) KNO3

When we say "stable" what does that mean?

Stable means less likely to react with another element

These are the steps for naming ionic compounds

Steps for naming ionic compounds\Positive Ion 1)The ending is -ide unless you have a polyatomic negative ion (those endings don't change) 2)more positive (less electronegative) one comes first Examples: MgO Magnesium Oxide

What does the number of valence electrons in an atom of an element determine?

The number of valence electrons in an atom of an element determines the properties of that element, including the ways in which the atom can bond with other atoms. ONLY valence electrons bond.

When you go to write a chemical formula for 2 elements that are bonding , which element goes first in the formula?

The positive one; Examples: MgO Magnesium Oxygen: Chemical formula=Magnesium Oxide

what is a chemical reaction? What is actually happening in a chemical reaction?

The process that substances undergo to become new substances. -Electrons rearrange -Chemical bonds are broken and formed

Which is strongest: Single,double, or triple covalent bonds?

Triple bonds are strongest because they share the most. Every time you share electrons you pull them closer. (like holding on with two hands is stronger bond than holding on with one hand- if we could hold on with three hands that would be even stronger!!)

What are valence electrons?

Valence electrons are the outer electrons of an atom and are held most loosely.

How does an atom become a negative ion?

When an atom gains an electron, it gains a negative charge and becomes a negative ion.

How does an atom become a positive ion?

When an atom loses an electron, it loses a negative charge and become a positive ion.

when atoms react (reactivity), what do they actually do?

When atoms react they form chemical bonds with other atoms

what is a neutral atom?

a neutral atom is an atom where there is the same number of protons and electrons

Where on the periodic table in each square do we find the charge (of the ion of that element)?

in the box on the right top corner