CH 4,5,6,7 Chem Test

Definition of an ATOM

Definition of an ATOM

the basic unit of a chemical element and is mostly empty space

Structure of the atom

the nucleus (protons[+] + neutrons[0]) electron cloud (space around the nucleus where electrons[-] can be found)

Dalton's Theory (4 Postulates)

1. All MATTER is made of small indivisible particles called atoms

2. Atoms of the same element are identical

3. Atoms can combine to form COMPOUNDS

4. In chemical reactions atoms are rearranged and no new atoms are created or destroyed

Calculate number of protons

#p+=Z

Calculate number of electrons

#e-=#p+ - charge

Calculate number of neutrons

A-Z

Atomic Mass (A)

A = p + n / A = Z + n

Atomic Number (Z)

Z=#p+ - is the whole number

Find the charge

charge = #protons - #electrons

How heavy is the nucleus compared to the whole mass of the atom?

It contains almost all the atom's mass and is the heaviest part of the atom

How big are e-, p+, n0 ?

Electrons are 10 thousand times smaller than neutrons and protons; neutrons and protons are the same mass

What are isotopes? How do we differentiate them?

atoms of the same element with same number of protons, but different number of neutrons

Calculate the average atomic mass

(% isotope1) x am1 +(% isotope2) x am2 ...

ions

they are atoms with charges anions (-), nonmetals and they gain electrons cations (+), metals and they lose electrons #p not + #e

Mendeleev and Newland on the Periodic Table

Newland arranged elements in the increasing order of atomic masses, every 8th element had similar properties, knew about noble gases but not discovered, forced elements to fit in a pattern Mendeleev used cards to arrange elements in order of increasing mass, found a pattern of repeating properties, elements grouped in columns if they had similar properties, inconsistencies in properties, gaps due to undiscovered elements, predicted their properties before they were found

A group vs a Period

A group a column of the Periodic table A period is a row of the Periodic table

properties of metals

easily lose electrons, corrode easily luster, good conductors of heat and electricity, high density, high melting point, ductile, malleable

properties of nonmetals

tend to gain electrons no luster, poor conductor of heat and electricity, brittle, not ductile, not malleable, low density, low melting point

properties of metalloids

solids, can be shiny or dull, ductile, malleable, conduct heat and electricity decently

Atomic Radius

half the distance between two nuclei of a diatomic molecule decreases --> increases v

Ionic Radius

Ions get bigger as you go down the group, across the period nuclear charge increases so they get smaller.

Cations

form by losing electrons and are smaller than the atom they come from; metals

Anions

form by gaining electrons and are bigger than the atom they come from; nonmetals

Ionization Energy

the energy needed to remove an electron from the outer shell of a neutral atom; increases --> decreases v

Electronegativity (Nonmetallic Character)

the tendency for an atom to attract electrons to itself when it is chemically combined with another element (not noble gases) increases --> decreases v

Electropositivity (Metallic Character)

The ability of an element to give away the outermost electrons and form cations decreases --> increases v

Reactivity

Metals are very reactive so the lower the IE, the higher the reactivity while nonmetals are more reactive than metals because they have a higher value of IE ; increases (nonmetals) --> increases (metals) v

Exceptions to Aufbau Principle

d4, f6, d9, f13