2.1 Atomic Structure - Theory & Introduction to the Periodic Table Flashcards
combining atoms of different elements =
compounds
Can atoms be destroyed
no
Whats at the center of the atom?
Nucleus
* Protons / Neutrons here
Protons = positive
Neutrons = neutral
All the mass of the atom is here (electrons have negligable mass)
3 subatomic particles
1) Electrons -
2) Protons +
3) Neutrons (neutral)
What units do we use to measure charge
Coulmb
how muhc charge does an electron and a proton have in C
e- = -1.602x10^-19 C
p = +1.602x10^-19 C
Protons / Neutron both weigh ~1amu
Electron = 1/2000 of an amu = negligable
dont memorize these
What is the bottom number (8)
automic number
* this is the number of protons in the atom - for oxygen it has 8 protons
these are written directly above on the periodic table
What is the automic number?
The number of protons in the atom
What is the 16?
this is the mass number
note for every atom there must be the same number of protons (oxygen always has 8 protons) however, the neutrons may vary (meaning oxygen could have 8 neutrons or 9 etc…). SO every atom isnt exactly identifcal - when neutrons vary they’re called isotopes
1amu = 1proton. so if you know the automic mass (oxygens most common istope is 16) than you can figure out how many protons cna neurons it has
* i can look at the automic # and see oxygen has 8 protons - I can look at the mass number and know that 8 of those are protons (weighing 8amu) - so the other 8amu must be the neutrons
if it was the isotope oxygen 17 that would mean that oxygen had 8 protons (because if its oxygen it must have 8 protons) and the other 9 amu must be neutrons.
Isotope meaning
A version of an element that has the same number of protons (which determines the element so this has to always be =) but a different number of neutrons
* for instance w/ O2 you always have 8 protons but the neutrons can vary - making there be different versions (or isotopes) of the atom oxygen
* However, the most common version is isotope 16
This -2 charge indicates that theres an imbalence between protons and electrons
* if tis a -2 charge there must be 2 more electrons than protons
What is a charged atom called?
Ions
Cation
Positively charged ion
Anion
negatively charged atom
KNOW: the mass number corresponds to an individal isotope
atomic weight/mass on the periodic table (different than the above) –> this is an average of all the masses of all the nautrally occuring isotopes
* for O2 its 15.999
* rememebr there are multiple isotopes of oxygen (varying neutron count but not proton) think taking the vaerage of all the oxygen 16’s and oxygen 18’s etc…
Br has mostly 2 naturally occuring isotopes (again meaning the number of neutrons vary)
79Br and 81Br
* **it turns out about 50% are 79Br and 50% are 81Br - so the atomic weight listed on the periodic table is 79.9 –> because its an average weight of all the nautrally occuring isotopes. **
So when the atomic weight is not near 1 whole number that means theres not 1 main isotope. It means theres at least 2 major ones and this again is the average mass of all the isotopes
so for instance the atomic weight for cl is 35.45, meaning that theres at least 2 isotopes that are contributing to this (because its not one whole number)
well the two main ones at 35cl and 37cl. We can see that its much closer to 35 than 37 so we can decide that 75% are 35cl and 25% are 37cl.
how we actually calculate the real mass is
(.075)(35) + (0.25)(37) = 35.5amu
remember 1 proton = 1amu
1 neutron = 1amu
what is a group?
columns
* aka up and down
these are called groups - and we group together things that have similar properties
* so up and down they have the same valence electron count
What are periods
these are the rows or L/R
Think of something peridoc like the sun rising (happens every 24 hours) is horizontal just like this ez pz
you will also run into the same thing in periods
* for instance noble gases dont react much and you periodically run into them when going horizontally across the periodic table
everything to the left of that stair case is a metal and everything to the right is a non metal
everything right along that stair case (really anything touching the red bolded line) are called the semi metals or metaloids
* these have some properties of metals and some properties of non metals
What are metaloids?
Things along that stair case where metals transition to non metals
they have properties of both metals and non metals
Group 1 and 2 (vertical) all the way to the left
Group 7 and 8 (sometimes called 17 and 18) are the last 2
Group 1 are called what
alkali metals
Group 2 names
alkaline earth metals
Group 7 name
Halogens
Group 8 name
Noble gases
these dont react much w/ other things because they have a full valence shell
The things between where he has his hands are transition metlas
* basically everything between group 2 and 3
lanthanides and actinides are at the bottom of the periodic table and are considered the heavy metals
* they sunk to the bottom
Chloriene-37 refers to the isotope of chlorine with a mass number of 37. This gives the total sum of protons and neutrons. Chlorines anatomic # is 17 meaning it has 17 protons. Therefore chlorine 37 has 2- neutrons (37-17 = 20)
how many electrons are present on an iron atom?
26
* i can look up how many protons it has and match the electrons because atoms have no charge
how many electrons are present in Fe2+
26 protons has a 2+ charge so must be missing 2 electrons = 24
How many neutrons are present in iodine-126
iodine has 53 protons
126-53 = 73 neutrons
what is the atomic mass of fluorine?
19.00 listed on periodic table
* its the average mass of all the isotopes
What is the formula wt for Ca(NO3)2
CaNO3NO3
