Unit 5

Question 1

emission of energy by atoms

Answer 1

when atoms receive energy, they become excited. they can release the energy by emitting a light. the emitted energy is carried away by a photon

the energy of the photon corresponds exactly to the energy change of the emitting atom

high energy photons correspond to short wavelength light. low energy photons correspond to long wavelength light

the photons of red light have less energy than the photons of blue light cuz red light has a longer wavelength than blue light

Question 2

energy levels of hydrogen

Answer 2

when we study the photons of visible light emitted, we only see certain colors

only certain types of photons r produced

because only certain photons r emitted, only certain energy changes r occurring

so, hydrogen atoms must have certain discrete energy lveles

we say the energy levels of H r quantized, that is, only certain values are allowed

energy levels of all atoms r quantized

Question 3

hydrogen orbitals

Answer 3

the probability map is called an orbital. the orbital shown in the pic is called the 1s orbital & describes the ground(lowest) state of energy for H

size of orbital is defined by a sphere that contains 90% of the total electron probability

Question 4

principal energy levels

Answer 4

discrete energy levels

designated by whole #’s symboized by n; n can equal 1, 2, 3, 4,… level 1 corresponds to n = 1, etc.

energy of teh level increases as value of n increases

describe size & shape. the s orbital is spherical. level 1 is smaller than level 2, which is smaller than level 3.

each principal energy level contains 1+ types of orbitals, called sublevels

Question 5

sublevels

Answer 5

the # of sublevels present in a given principal energy level equals n.

Ex: level 1 contains one sublevel (1s); level 2 contains 2 sublevels (2 types of orbitals), the 2s orbital and the three 2p orbitals; and so on.

These are summarized in the pic. the # of each type of orbital is shown in parentheses.

n value always used to label orbitals of a given principal energy level & followed by letter tht indicates the type (shape) of the orbital

Question 6

wave mechanical model

Question 7

orbital

Answer 7

can be empty or can contain 1/2 electrons, but never more than 2

if 2 electrons occupy same orbital, must have opp spins

shape of an orbital doesn’t indicate the details of electron movement. merely indicates the prob distribution for an electron residing in that oribtal

Question 8

spin

Answer 8

each electron appears to spin like a top on its axis

can only spin in 1 direction. we represent spin with up & down arrows.

Question 9

Pauli Exclusion Principle

Answer 9

an atomic orbital can hold a max of 2 electrons & those 2 electrons must have opp spins

Question 10

electron configuration

Answer 10

principal energy level followed by sublevel; # of electrons in the orbital placed as superscript

Ex: 1s¹

Question 11

orbital diagram

box diagram

Answer 11

Question 12

valence electrons

Answer 12

the electrons in the outermost (highest) principal energy level of an atom

these r the electrons involved in bonding of atoms to each other

the atoms of elements in the same group have the same # of electrons in a given type of orbital, except that the orbitals are in diff princ energy levels. (except He, which is 1s)

elements w/ same valence electron arrangement show very similar chem behavior

Question 13

orbital filling

Answer 13

in a principal energy level that has d orbitals, the s orbital from the next level fills before the d orbitals in the current level. That is, the (n + 1)s orbitals always fill before the nd orbitals.

Ex: the 5s orbitals fill for rubidium & strontium before the 4d orbitals fill

Question 14

lanthanide series

Answer 14

after lanthanum, which has configuration [Xe]6s²5d¹

a group of 14 elements

corresponds to the fillling of the seven 4f orbitals

Question 15

actinide series

Answer 15

after actinium, [Rn]7s²6d¹

14 elements

corresponds to filling of seven 5f orbitals

Question 16

bond

Answer 16

a force that holds 2+ atoms together & makes them function as a unit

In water, the fundamental unit is the H-O-H molecule, which is held together by the two O-H bonds

Question 17

ionic compounds

Answer 17

formed when an atom that loses an electron relatively easily reacts w/ an atoms that accepts an electron

when metal reacts w/ non-metal

resulting bonds = ionic bonds

electrons transferred

Question 18

covalent bond

Answer 18

when 2 similar atoms form a bond, the electrons r equally attracted to the nuclei of the 2 atoms

electrons shared by nuclei

Ex: diatomic hydrogen H-H

Question 19

polar covalent bonds

Answer 19

b/w the extremes

atoms r not so diff that electrons r transferred, but diff enough tht unequal sharing of the electrons results

Question 20

electronegativity

Answer 20

the unequal sharing of electrons b/w 2 atoms is described by this property

the relative ability of an atom in a molecule to attract shared electrons to itself

the higher the electronegativity value, the closer the shared electrons tend to be to that atom when it forms a bond

F has highest electronegativity & so always polar

increasing electronegativity as goes right and up

Question 21

polarity

Answer 21

depends on the diff b/w the electronegativity values of the atoms forming teh bonds

if similar electronegativites, the electrons r shared almost equally & bond shows little polarity

if very diff electronegativies, very polar bond is formed

Question 22

stable electron configurations

Answer 22

representative (main-group) metals form ions by losing enough electrons to attain the configuration of the previous noble gas tht occurs before the metal

nonmetals form ions by gaining enough electrons to attain the configuration of the next noble gas

when a non-metal & a Group 1, 2, or 3 metal react to form a binary ionic bond, the ions form so that the non-metal completes the valence-electron config of the next noble gas & the metal empties the valence orbitals to achieve the config of the prev. noble gas

when 2 non-metals react to form a covalent bond, share electrons in a way that completes the valence-electron configuration of both atoms

Question 23

Lewis structures

Answer 23

bonding involves just the valence electrons. this structure is a representaiton of a molecule tht shows how the valence electrons r arranged among the atoms in the molecule

H - duet rule

He - doesn’t form bonds cuz valence orbital already filled

2nd row nonmentals C thru F - octet rule

Ne - doesn’t form bonds cuz already has an octet of valence electrons

1. Obtain sum of the valence electrons from all of the atoms.
2. use 1 pair of electrons to form a bond b/w each pair of bound atoms. Use line.
3. arrange the remaining electrons to satisfy the duet rule for hydrogen & the octet rule for each 2nd-row element (may need to guess & check w/ double bonds, etc.)

Question 24

duet rule

Answer 24

H forms stable molecules where it shares 2 electrons

Question 25

octet rule

Answer 25

2nd-row nonmetals C through F form stable molecules when r surrounded by enough electrons to fill the valence orbitals - that is, the one 2s and the three 2p orbitals.

8 electrons required to fill these orbitals

Question 26

configuration tips

Answer 26

noble gas valences from top to bottom:

1s²

2s²2p⁶

3s²3p⁶

4s²4p⁶

5s²5p⁶

6s²6p⁶