Molar Mass
What is the mass of 1 mole of Oxygen?
15.99 g
15.999 g
16.00 g
What does the atomic number tell us?
# of protons
What are the two ways we classify periodic trends?
1. down a group
2. across a period
What is the chemical symbol of iron?
Fe
How many electrons does group 4A have?
4
How do you calculate the molar mass of a compound?
Add each of the elements' atomic masses together
What is the name of group 1A?
Alkali metals
What is the most electronegative element? Least?
Most: Fluorine
Least: Francium
If the molecular formula of a compound is C3O6, what would the empirical formula be?
CO2
How do you calculate atomic mass?
protons+neutrons
If I have 50.00g of N, how many moles of N are there?
about 3.6 moles
What kind of elements are to the left of the staircase?
metals
What is the atomic radius trend down a group? Why?
If the empirical formula of a compound is H2O, what could the molecular formula be?
answers may vary
(ie: H4O2, H6O3, H8O4, H16O8)
Why do we exclude noble gases from the electronegativity trend?
Noble gases have a full valence shell so they do not want to attract electrons toward them. They are stable!
What is the molar mass of K2SO4?
about 174 g
What group reacts best with group 1A and why?
7A because when these groups react, they have the exact number of electrons to fill the valence (outermost) shell.
What is the atomic radius trend going across a period? Why?
It decreases because as you go across a period, the number of valence electrons increases, so the more valence electrons, the greater the pull toward the positively charged nucleus.
What is the percent composition of oxygen in H2CO3?
about 77%
Name three elements in the halogens
fluorine, chlorine, bromine, iodine, astatine
What is the molar mass of 5 moles of NaNO3
about 425 g
Why is the calculated atomic mass different than the one listed on the periodic table?
The atomic mass on the periodic table is an average of all of the known isotopes, while the calculated atomic mass only takes into account 1 isotope.
What are the trends of electronegativity? Why?
Down a group: decreases because as you go down a group, the number of electron shells increases, so the further down the group, the harder it is to attract electrons
Across a period: increases because as you gain valence electrons going across the period, the easier it is to attract electrons because there are more electrons available to attract.
SrO2
down a group: decreases because as the number of electron shells increases, the less energy required to remove an electron
across a period: increases because as the numer of valence electrons increases, the more energy required to remove an electron