Chemistry Sept 28

periodic law

periodic law

the principle that chemical properties of the elements are periodic functions of their atomic numbers

groups or families

vertical columns

periods

horizontal rows

octet rule

the tendency to acquire a total of 8 valence electrons

isoelectronic

having the same numbers of electrons or the same electronic structure.

ion

a particle that is electrically charged; an atom or molecule or group that has lost or gained one or more electrons

metals

typically cations - positively charged

non-metals

typically anions - negatively charged

multivalent ions

usually transition metals may form ions with more than one charge

polyatomic ion

a group of atoms covalently bonded that carry a charge

alkali metals

group 1

halogens

group 17

noble gases

group 18

isotope

one of two or more atoms with the same atomic number but with different numbers of neutrons

average atomic mass

average mass of several items. Weighted average.

radioisotope

Some isotopes of atoms are very unstable. A radioactive isotope of an element; is produced either naturally or artificially.

problems in rutherfords model

why the protons in the nucleus didn’t repel each other

why the electrons in orbit didn’t spiral into the nucleus

the unique line spectra of elements

energy levels

Each orbit is called an energy level since it has a specific amount (quanta) of energy associated with it Normally, electrons that exist in those energy levels are if an electron absorbs additional energy, then it can be “promoted” from a lower energy state to a higher energy state and is then in an unstable state - EXCITED STATE

Staircase idea

when the electron “falls” back to its original ground state it releases energy in the form of light

different sized “falls” = different amounts of energy released = different colours in the spectrum = a “fingerprint” of the element’s unique electron arrangement

SMALL jumps down = less energy released (lower energy ~ lower frequency ~ longer ) = toward red end of the spectrum LARGE jumps down = more energy (higher energy ~ higher frequency~ shorter λ) = toward violet end of spectrum

OVERCOMING the ISSUES of RUTHERFORD’S MODEL

The existence of a “strong nuclear force” , which is greater than the electrostatic force of repulsion Electrons are stable since they are quantized Each element has its own particular, organized electron arrangement, therefore its own unique emissions spectrum

new, highly mathematical atomic model

Quantum Mechanical Model

Quantum Mechanical Model and Energy:

Electrons occupy specific energy levels/shells in an atom. The number of electrons in each level is governed by the formula 2n2. Schrodinger proposed that the atom was arranged as “layers within layers” in terms of the electron shells.Schrodinger also proposed that an electron behaves in a waves manner rather than just as particles. Thus, electrons are both particles and waves at the same time.Since electrons are waves, they do no remain localized in a 2-D orbit. Instead of being organized in 2-D orbits, electrons are actually found in 3-D orbitals. Each orbital defines an area where the probability of finding an electron is high. These orbitals are known as electron clouds.

orbits

2d path

fixed distance from nucleas

circular or elliptical path

2n2 electrons per orbit

orbitals

3d path

variable distance from nucleus

no path; varied shape of region

2 electrons per orbital

orbital sublevels

“s” “p” “d” “f”

s

Spherical s orbital 2

p

Perpendicular p orbital 6

d

Diffuse d orbital 10

f

Fundamental f orbital 14

Pauli Exclusion Principle

each orbital can hold 2 electrons with opposite spins “opposite direction rule”

Aufbau Principle

electrons fill the lowest energy orbitals first “lazy tenant rule”

start at the top and add electrons in the order shown by the diagonal arrows this is known as “Order or Filling”

Aufbau order

1s,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d,6p,7s,5f,6d,7p

Hund’s Rule

Within a sublevel, place one e- per orbital before pairing them “Empty Bus Seat Rule”

orbital diagram

boxes and from right to left

energy level diagram

from bottom to top with "seats"

def. of physical properties

characteristic of a substance that can be observed or measured without changing the identity of the substance.

malleability

the property of being physically malleable; the property of something that can be worked or hammered or shaped without breaking

solubility

the quantity of a particular substance that can dissolve in a particular solvent

ductility

the malleability of something that can be drawn into threads or wires or hammered into thin sheets

physical properties EXs

color, hardness, malleability, solubility, electrical conductivity, density, melting points, and boiling points

chemical property definition

a property used to characterize materials in reactions that change their identity

chemical property examples

flammability, toxicity, acidity, reactivity (many types), and heat of combustion

atomic radii def.

he total distance from an atom's nucleus to the outermost orbital of electron

atomic radius trend

generally decreases from left to right across a period and increases down a group

ionization energies def.

a measure of the energy needed to pull a particular electron away from the attraction of the nucleus

ionization energy trend

increases as you move left to right across a period and decreases down the group.

covalent bonds tend to be:

gases or liquids Covalent compounds are insoluble in water low melting and boiling points good conductors brittle

ionic bonds tend to be:

solids are soluble in water have high melting points are bad conductors brittle

does 2.852 x 10^3 round up or down

down

homogeneous mixture

a mixture of substances blended so thoroughly that you cannot see individual substances

mechanical mixture

a mixture whose components are separable by mechanical means as distinguished from a chemical compound

compound

a chemical substance composed of many identical molecules containing atoms from more than one chemical element held together by chemical bonds.

heterogeneous mixture

a mixture where throughout the solution the composition is not uniform.

pure substance

a single kind of matter that cannot be separated into other kinds of matter by any physical means

is mass number rounded to the nearest digit or hundredth

nearest hundredth

electron affinity

The amount of energy released when an electron attaches to a neutral atom or molecule in the gaseous state to form an anion.

polar

a molecule that has a charge on one side of the molecule, that is not cancelled out