introduction to chemistry

Question 1

columns are known as - on periodic table

rows are called -

Answer 1

groups

periods

Question 2

explain groups in periodic table

Answer 2

• elements in each group have similiar but not identical properties
• for ex- lithium, sodium, potassium are all soft white shiny metals
• all elements have same number of electrons in their shell

Question 3

explain periods

Answer 3

• elements in a period are not alike in properties
• properties change greatly across every given row
• first element in period is always a reactive solid
• last element is always an unreactive gas(noble)

Question 4

what about hydrogen?

Answer 4

• has unique size so does not act like member of group 1
• is a gas at room temp
• has one proton and one electron in its one and only energy level
• needs 2 electrons to fill up its shell

Question 5

no of valence electrons means?

Answer 5

no. of valence electrons corresponds to the last digit of the group number
ex- group 14 has 4 valence
group 2 has 2 valence

Question 6

what is atomic radius

Answer 6

total distance from an atoms nucleus to the outermost shell

Question 7

what is ionization energy

Answer 7

energy required to remove the outermost electron, ionization energy increased across a period and decreases top to bottom.

Question 8

the nucleus is-

Answer 8

made up of protons and neutrons
positively charged because of protons
dense- contains nearly all the mass of atoms in a tiny space

Question 9

electrons are?

Answer 9

very small and light
negatively charged
able to be lost or gained in chemical reactions
found thinly spread around outside of nucleus orbiting in shells

Question 10

first shell is?

Answer 10

inner shell- shell closest to nucleus

Question 11

what is electron configuration

Answer 11

the arrangment of electrons in shells

Question 12

what is bohr model used to?

Answer 12

to represent an atomic model

Question 13

what are valence electrons

Answer 13

electrons in outermost shells
repsonsible for atomic bonding
equal to the last digit of the group number

Question 14

orbitals-

Answer 14

electrons dont really exist in shells, rather in clouds around the nucleus
since the electron cloud has no specific boundary, we show most probable area(based on orbitals)
the different energy levels that electrons can exist in are called shells

Question 15

pauli exclusion principle

Answer 15

an orbital can only hold 2 electrons with opposite spins

Question 16

hunds rule(bus rule)

Answer 16

electrons enter orbitals singly until they have to pair up

Question 17

electron filling order

Answer 17

electrons fill the shells at lower energy first before filling shells at higher energy levels

Question 18

Relative atomic mass

Answer 18

mass of one of its atoms relative to 1/12 the mass of one atom of carbon-12