Molecules and Cells: Atoms and Bonds

2.3, 2.5, and 2.6 - 2.8

Atom

Smallest unit of matter

Proton

A positively charged subatomic particle found in the nucleus of an atom

An atom has 3 subatomic particles (categories). What are they?

Protons, neutrons, electrons

Neutron

A subatomic particle with no charge. It is found in the nucleus of an atom.

Electron

A negatively charged subatomic particle that lives in the electron cloud of an atom.

What two subatomic particles make up the nucleus?

Neutrons and Protons

Atomic number is equal to…

the number of protons in an element

Mass number

The sum of the number of protons and neutrons in an atoms nucleus. (P+N=Mass #)

Atomic Mass

Approximately equal to the mass number (written below the element name on the periodic table. ex: Carbon AM=12.0107)

Isotope

The same element (ex: Carbon) has same number of protons and behave identically in reactions, but have different number of neutrons. (ex: Carbon-12, Carbon-13, Carbon-14)

Nucleus of an atom

the dense center of an atom made up of protons and neutrons

What is a nucleus’ charge?

positive due to the positively charged protons.

Molecule

Two or more atoms held together by covalent bonds

covalent bond

Sharing of electrons between atoms to complete both atoms outer electron shells.

What are the two types of covalent bonds?

polar and nonpolar

Inert

A full ring of electrons. Does not interact with other electrons from other atoms. (the outermost ring is complete with 8 electrons)

Electronegativity

A measure of attraction for shared electrons. (How much one atom pulls the other in)

weak attraction=low electronegativity, strong attraction=high electronegativity

Polar covalent bond

two atoms of different electronegativity. The electrons are shared unequally

Nonpolar covalent bond

Atoms of the same element share electrons equally because they have the same electronegativity. Atoms of different elements with similar electronegativity also share electrons fairly equally

noncovalent bond

A bond formed between molecules

Where are covalent and noncovalent bonds formed?

Covalent: between atoms

Noncovalent: between molecules

Ionic bond

Transferring of electrons

hydrogen bonds

Weak attractions between unequally charged molecules

Types of noncovalent bonds

Ionic, Van der Waals interaction, and hydrogen bonds

Using the electron distribution of first 18 elements on periodic table, how many covalent bonds can each atom form? Hydrogen, oxygen, nitrogen, and carbon

H: 1 O: 2 N: 3 C: 4

Van der Waals interactions

weak, electrical pull between nearby molecules or atoms

Formula for finding charge

Charge=p-e

Ion

An atom or molecule with an electrical charge from a gain or loss of electron(s)

Negatively charged ions typically end in…

-ide

double covalent bond

sharing of two electrons

carbon and hydrogen atoms are weak/strong attraction

weak

oxygen and nitrogen are weak/strong attraction

strong

to determine which atoms have charges what do you need to know?

location of nonpolar vs polar covalent bonds

covalent bonds

connect atoms to form a molecule

noncovalent bond

interactions between atoms with opposite charges

• atoms can be in different molecules or the same molecule

• weaker than covalent bonds

three main types of noncovalent bonds

ionic, van der waals, hydrogen

ionic bonds

atoms with FULL opposite charges

ionic bonds are weaker than covalent bonds

hydrogen bonds

partially positive hydrogen and atom with partial negative charge

van der waals interactions

atoms with VERY TEMPORARY partial opposite charges (connected by nonpolar covalent bonds, so not normally charged)

covalent bonds determine…

shapes of smaller molecules and properties

-electronegativities of atoms determine if bonds are nonpolar or polar, which atoms (if any) have charges

noncovalent bonds

• determine the 3D shapes of larger molecules and allow them to change shape

• allow molecules to interact with each other

• can provide amazingly strong interactions (MANY weak chemical bonds = STRONG force)

Could two molecules contain the same sets of atoms but have different properties?

Yes, because atoms can be arranged in different ways, creating molecules with different structures and properties.