The columns of the periodic table, also referred to as "groups" contain elements with similar reactive properties, due to these elements having a similar configuration of electrons in their outer shell.
A teaspoon of caffeine is <em>NOT</em> deadly as teaspoon of ricin
Answer:
Explanation:
alright, dawg, lets get this bread. CHEMISTRY? OH YEAH I LOVE CHEMISTRY.
what is a mol? do you know who avogadro is? sounds like avocado. free shavocado. ok so you MUST REMEMBER THIS NUMBER PLEASE.
please remember this number and commit it to your memory: avogadros number

this is how much a mole is. you know how a pair is 2 and a dozen is 12? ok so a mole is
it is confusing at first but hopefully this helps you to understand.
now that we understand this..... lets perform this calculation with a calculator

notice i divide the question by the avogadros number to find out how many moles are in the number. ok but listen... it gets into a tough area here... because HOW ARE WE TO DIVIDE SUCH A HUMONGOUS NUMBER BY ANOTHER HUMONGOUS NUMBER?!?!?
its easy, its cake, just listen this is how you do it. only focus on the numbers NOT the 10 exponential ones. so just 3.90 and 6.02 ok? lets divide these two numbers 3.90 / 6.02 and we get 0.6478... how interesting... ok now lets deal with the exponents of 10. notice that we are DIVIDING these numbers so think of it as subtracting the exponents of ten..... 22 minus 23 equals -1
so we have 
now this negative 1 thing is annoying so lets just make it to the power of 0

and anything to the power of 0 just becomes 1.
0.06478
so this is our answer but keep in mind we need 3 sig figs. if we round then we get 0.0648
put this into scientific notation we get 
Answer:
Explanation:
1 mol of methane = 6.02 * 10^23 molecules
6.70 mol of methane = x
Cross multiply
x = 6.70 * 6.02 * 10^23
x = 4.033 * 10^23 molecules.
Answer:
2.04 x 10²⁴ molecules
Explanation:
Given parameters:
Mass of Be(OH)₂ = 145.5g
To calculate the number of molecules in this mass of Be(OH)₂ we follow the following steps:
>> Calculate the number of moles first using the formula below:
Number of moles = mass/molarmass
Since we have been given the mass, let us derive the molar mass of Be(OH)₂
Atomic mass of Be = 9g
O = 16g
H = 1g
Molar Mass = 9 + 2(16 + 1)
= 9 + 34
= 43g/mol
Number of moles = 145.5/43 = 3.38mol
>>> We know that a mole is the amount of substance that contains Avogadro’s number of particles. The particles can be atoms, molecules, particles etc. Therefore we use the expression below to determine the number of molecules in 3.38mol of Be(OH)₂:
Number of
molecules= number of moles x 6.02 x 10²³
Number of molecules= 3.38 x 6.02 x 10²³
= 20.37 x 10²³ molecules
= 2.04 x 10²⁴ molecules