nature of chemistry 1

Question 1

Chemistry

Answer 1

study of matter, interactions involves experimenting in macroscopic world and theorizing about microscopic world

Question 2

Empirical knowledge

Answer 2

comes from investigation and observation

Question 3

Theoretical knowledge

Answer 3

Explains scientific observation: based on ideas created to explain

Question 4

Theory

Answer 4

explanation /model based on observation reasoning experimentation
- why something happens
predicting

Question 5

Law

Answer 5

explain observation either as statements or mathematical equation
-proven consistently

Question 6

What did greek philophers discover?

Answer 6

• matter can be subdivided into tiny particles calle atomos(cant be cut )

Question 7

Democritus

Answer 7

atom exsistence
different sizes,constant motion

Question 8

Aristole

Answer 8

matter is made up of earth, water ,fire, air

Question 9

Dalton

Answer 9

Law of conservation of mass
- atoms are rearranged to form new substances but never created or destroyed

Question 10

JJ thompson

Answer 10

-used a cathode ray tube to discover the existence of electrons
- electrons are small (-) particles(plum pudding model)

Question 11

Rutherford

Answer 11

nuclear model
- aimed + alpha particles at gold foil and measured how many alpha particles deflected off the foil on a fluorescent screen
COnclusions:
most were absorbed by foil and only some were deflected
Nuclear model: atom contains small dense positive centre

Question 12

Chadwick

Answer 12

Exsistnece of the neutron confirmed

Question 13

Bohr

Answer 13

Electrons existed in energy levels
Planetary model: electrons orbit the nucleus in definite energy levels (shells) can jump and transfer.

Question 14

Ground state

Answer 14

when electrons in an atom have the lowest amount of energy possible for the location that they are at in the element

Question 15

Excited state

Answer 15

when energy is added in the form of heat or electricity to an atom
electrons absorb energy which allows them to jump to a higher energy level

Question 16

Emission spectrum

Answer 16

pattern of electron movement= ands of certain wavelengths of coloured light
- used to identify unknown samples
purple= far electron jump
red= short electron jump

Question 17

Isotope

Answer 17

atoms of the same element that have different # of neutrons but same p and e-

Question 18

isotopic abundance

Answer 18

the % of a given isotope in a sample of an element

Question 19

Radiation and radioisotopes

Answer 19

• some isotopes are stable while others break
• difference in stability is due to the composition of the nucleus
• large # of neutons destabilize the nucleus

Question 20

Alpha particles

Answer 20

same structure as helium nucleus with a 2+ charge
- blocked by paper

Question 21

Beta particles

Answer 21

-negatively charged e-
- blocked by aluminun

Question 22

gamma rays

Answer 22

have no mass and travel at light speed blocked by lead

Question 23

trend

Answer 23

predictable change in particular direction

Question 24

electron shielding

Answer 24

inner electrons shield outer electrons from the full attractive force of the nucleus(protects valence shall from attraction

Question 25

effective nuclear charge

Answer 25

charge felt by valence electrons after you have taken into account the # of shielding electrons

Question 26

atomic radius

Answer 26

distance from center to outmost orbit

Question 27

what happens to atomic radius as you move down the group ?

Answer 27

it increases as the electrons occupy consecutiveley higher energy levels farther from nucleus
- ENC decreases due to increased shielding

Question 28

what happens as you move across a period to radius?

Answer 28

atomic radius decreases
- same number of orbits electrons are in same energy level
-more nuclear charge (protons added moving left to right)
- outermost electrons are pulled closer

Question 29

what happens when you move down a group to ionization?
what happens when you move across a period?

Answer 29

decreases due to increased electron shielding and decreased ENC
- increases as you move across period, increas in ENC unchanged shielding

Question 30

Electron affinity

Answer 30

the energy given off when an electron is added to atom to make an anion
- high affinities form negative ions in IC
- low affinities form positive ions in IC

Question 31

EA trends

Answer 31

• decreases as you move down group due to increased electron shielding and decreased ENC
• increases as you move across a period
  due to increasing nuclear charge unchanged shielding easy to gain e-

Question 32

Electron negativity

Answer 32

measure of the ability of an atom in a compound to attract electrons in a bond
- higher electronegativity means a stronger pull on e-
- charges vary from 0-4

Question 33

Radius of cations

Answer 33

-metals form cations
- cations form by losing electrons
- cations smaller then og atom as they lose an energy level
- more e- lost = radius gets smaller
- enc increases, shielding decreases.

Question 34

radius of anions

Answer 34

-nonmetals form anions
- anions form by gaining electrons
- anions are bigger then og atom
- have the same energy level and nuclear charge but more repulsion
- radius get larger
ENC decreases shielding unchanged repulsion increases

Question 35

Ionic radius trends

Answer 35

-increases as you move down a group
- decreased ENC as shielding is unchanged
- decreases as you move across a period due to inccreasing nuclear charge
- + ions left to right =higher ENC
- - ions left to right ( less electrons are need to the right so e- and p count similar = less repulsion

Question 36

ionization energy

Answer 36

energy required to remove an electron from an atom or ion
- overcome attraction between e- and nucleus+

Question 37

2nd ionization energy

Answer 37

the energy required to remove a second electron from a cation
- needs more energy then 1st ionization as the nucleus became more + since first electron was lost

Question 38

ionization energy group 1

Answer 38

group 1: easily loses its 1 valence e-
- low first ionization energy
- second ionization will be very high since the new valence is full

Question 39

ionization group 2

Answer 39

• easily loses 2 valence e -
• low first and second ionization energies
• high third ionization energy since new shell is full

Question 40

Electronegativity trends

Answer 40

• decreases as you move down a group due to decreases ENC and lots of shielding
• increases as you move across a period
  increasing atomic #, increase in ENC and unchanged shielding
  metals have low electronegativity
  nonmetals have high electronegativity

Question 41

dmitri medeleevs periodic law

Answer 41

when elements are arranged according to increasing atomic mass , periodic recurrence of properties occurs at regular intervlas

Question 42

Alkali metals

Answer 42

• column 1, 1 valence e-
• soft, silver, solids
• reacts violently to make base

Question 43

Alkaline earth metals

Answer 43

• column 2, 2 valence e-
• solid
• reacts with air to form oxide coatings
• reacts with hydrogen to form hydrades

Question 44

halogens

Answer 44

column 17 , 7 valence e-
- solid, liquid, gas
- dull and not a conductor
- very reactive

Question 45

noble gases

Answer 45

column 18 8 valence e-
- gases
- low melting and boiling point
- inert (unreative)