Chemistry Review

ELEMENTS OF LIVING MATTERELEMENTS OF LIVING MATTER

•OXYGEN•CARBON•HYDROGEN•NITROGEN

•OXYGEN•CARBON•HYDROGEN•NITROGEN

There are other elements that are important also…

• Potassium• Sulfur• Calcium• Phosphorus• Iron• Sodium

IN ANIMALS:

In some amino acids

In membrane functions & sending nerve impulses

Component of bones & co-factor in some enzymes

Phosphate groups in ATP

In hemoglobin (haemoglobin) & in cytochromes

Helps maintain the fluid & electrolytes in the body.

IN PLANTS:

co-factor in some enzymes

in cytochromes

HELIUM ATOM

ELECTRONS

PROTONS

NEUTRONS

NUCLEUS

ORBITALProton # changed= new elementElectron # changed= a charged ionNeutron # changed= an isotope

• How many electrons fit in each orbital?• How does the proton number compare to the

electron number?• What is the trend of electronegativity among

atoms?• How do you think the number of electrons on the

outer orbital of each atom relates to how stable the element is?

• Which elements are the most reactive?

Some discussion questions

2 on the s orbital and 8 on the next two p orbitals

They’re the same on an element if it is unaltered/uncharged

Increases from left to right across a row and decreases from top to bottom down a columnAtoms with full outer shells are more stable & less reactive; elements made of atoms with partially complete outer shells are more reactive; the closer the atom is to having a completely full or completely empty outer shell the more violently it reacts with other atoms.

The halogens; column VII

Isotopes• Is an atom with more neutrons than “normal”

– = greater mass

• Isotopes can be stable such as C-13 or they can be unstable like C-14.– C-14 is a radioactive isotope

• Its nucleus decays spontaneously, giving off particles of energy.• When the decay goes on long enough it will change the number of

protons which will then change to a different element.• EX: C-14 will change to N.

– What are some uses?• Fossil dating• Used as tracers• Provide high quality imaging of organs & detecting tumors…• Allow produce to have a longer shelf-life.

Ionic Bonding

• A strong bond• Opposite charge atoms bond & an electron is lost

by one atom & gained by the other.– Cation: when the charge of an atom is positive

• The atom lost an electron– Anion: when the charge of the atom is negative

• The atom gained an electron

Ionic Bonds

The formation of the ionic bond in table salt

NaCl Crystal

Everyday tablesalt

Which atoms are the anions & which are the cations?

LiCl

MgO

Discussion Questions• Which elements of the periodic table tend to become

negative ions (greatest potential for gaining an electron)? Why?

• Which ones tend to become more positive (have the weakest ability to keep their electrons)? Why?

• Which columns would combine well in order for both to be more stable?

• Which elements on the periodic table tend to make ionic bonds?

• How does electronegativity correlate with ionic bonding?• Why don’t all the elements of the periodic table form

ionic bonds?• What do atoms that cannot form ionic bonds do to

become more stable?

The atoms in column VII because they are only missing one electron & they have the high electronegativity needed to steal one from another atom

The elements to the far left in column I, because they have low electronegativity & have only 1 electron on their outer orbital

Columns I and VII, columns II and VI

Columns I and VII, columns II and VI

Atoms with high electronegativity are able to steal electrons most easily, atoms with low electronegativity tend to have their electrons stolen from themAt some point an element is unable to steal enough or give enough electrons in order to

become stable because it does not have enough electronegativity to steal as many electrons as it needs or it has too much electronegativity to give away as many as would be necessary.

Form a covalent bond

Covalent Bonding

HOW DOES THIS HAPPEN? WHY DOES THIS HAPPEN?

VERY STRONG BOND

Attraction of electrons to the protons

How do the valence electrons influence molecular bonding?

How does electronegativity influence molecular bonding?

The number of open places on the valence shell determines the number of bonds it can make.

A large difference between electronegativities of 2 atoms then the one w/higher electronegativity can steal electrons from the other. If both are fairly equal then they will form a covalent bond.

HOW MANY BONDS CAN THE FOLLWING ATOMS MAKE?

• HYDROGEN• OXYGEN• CARBON

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POLAR vs NONPOLAR

Nonpolar= when there is an equal sharing of electrons between two different atoms or because of the symmetrical arrangement of polar bonds.

Nonpolar= when there is an equal sharing of electrons between two different atoms or because of the symmetrical arrangement of polar bonds.

Polar= when one atom is bonded to another and the electronegativity is not the same causing the electron(s) of one atom to be shared unequally or the asymmetrical arrangement of the molecules

Polar= when one atom is bonded to another and the electronegativity is not the same causing the electron(s) of one atom to be shared unequally or the asymmetrical arrangement of the molecules

HYDROGEN BONDING: DRAW 2-3 MOLECULES OF WATER & INDICATE THE

HYDROGEN BONDS

HYDROGEN BONDING: DRAW 2-3 MOLECULES OF WATER & INDICATE THE

HYDROGEN BONDS

Formed by the attraction of opposite partial electric charges between two polar molecules

WEAK BONDSNot effective over long distances

Draw a hydrogen atom & fluorine atom (no need to worry about the neutrons & protons this time)

Draw a hydrogen atom & fluorine atom (no need to worry about the neutrons & protons this time)

WHICH ATOM WOULD BE CONSIDERED MORE ELECTRONEGATIVE? WHY?

HOW CAN THESE ATOMS BECOME MORE STABLE?

WHAT DO YOU CALL THIS?