Unit 1 Atomic Structure and Properties

Atomic mass unit (Amu)

1/12 the mass in carbon-12 used to express atomic and molecular weights. The mass of one mole of a substance (in grams) is numerically equal to its atomic or molecular mass (in amu).

Ex: 1 mol of copper is 63.55, g/mol is 63.55, amu is 63.55

How to calculate specific ions in a sample

1. Find moles of the whole subtance

2. Multiply by the amount of the ions we’re tryna find

3. multiply by avagadros number 6.022×10²³

ex: find Na ions in 10g of Na2SO4

1. 2(22.99)+32.06+4(16) =142.04g/mol 10/142.05= 0.0704 mol Na2SO4

2. two Na+ so.. 0.0704×2 = 0.141 mol Na+ ions

3. 0.141 × 6.022×10²³ = 8.48×10²² Na+ ions

How to find MASS of _ moles of an isotope

1. multiply number of moles by avagadro.

2. multiply by mass of the isotope in amu.

Ex: given isotope 1: mass 90 amu, relative abundance 51.34%. Find mass of 2 moles

1. 2(6.022×10²³)=1.2044×10²⁴

2. (1.2044×10²⁴⁾ × 90 = 1.083×10²⁶

How many atoms in 1 mol of copper?

6.022×10²³

The atoms in 1 mole of EVERY element is avogadros #

Isotopes have different ____ but same ____

Different neutrons, same protons

Calculate average atomic mass from isotopes

(atomic mass amu x abundance %) + (atomic mass amu x abundance %)

elemental analysis

-Finds how many atoms of an element in a compound

-Determine purity of a compound in a mixture

(Useful to find formula unit of a compound)

Different samples of a chemical compound always have the same ..

Composition of elements

What it means is that it doesn’t matter where the compound comes from, it will have the same % or ratio of elements each time

(Discovered by Joseph Proust)

Atomic Theory

1. All events composed of atoms

2. Atoms cannot be created/destroyed in a chemical reaction

3. Atoms of one element are different from another elements atoms. All atoms of an element are identical.

4. All compounds have a fixed ratio of atoms of elements

Made by John Dalton 1803

What was proven wrong of the Atomic Theory?

It is found that all atoms of an element are NOT identical!!

Isotopes exist!

How to find empirical formula of compound from its % of elements

1. Turn the percents into grams

2. Divide them by the element gfm to find moles

3. Divide every mol by the smallest mol

Empirical formula

LOWEST ratio of elements, simplest form

How to find MOLECULAR formula

If molecular mass is given…

1. Add up molar mass (GFM) for the compound

2. Divide it by given molecular mass

3. Multiply the empirical mass by the answer

Ex: Empirical formula C4H5N2O has molecular mass 194 amu.

C4H5N2O = 97 amu… 194/97=2. Multiply C4H5N2O by 2! = C8H10N4O2

How to find purity of compound in mixture? (Elemental analysis)

Option 1

% of elements in the compound ONLY / 100

Option 2

100%- contaminating element %

Ex: NaCl sample contaminated w/sulfur. Sample has 25% Na, 39% Cl, 36% S

Option 1: 100-36 S= 64% pure

Option 2: (25 Na + 39 Cl) / 100 = 64% pure

A sample contains 2 different elements that are bonded. Is it a mixture or a pure substance?

PURE SUBSTANCE!

If the elements are bonded it forms one species. If its only one species in a substance its uniform/pure.

If elements are NOT bonded, they are different species so mixture.

How many orbitals in sublevel s, p, and d?

s=1 orbital (since it can hold 2 e-) 1s²

p=3 orbitals (since it can hold 6 e-) 2p⁶

d=5 orbitals (since it can hold 10 e-) 3d¹⁰

f=7 orbitals (since it can hold 14 e-) 4f¹⁴

what is the e- config of Se?

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁴

or [Ar] 4s² 3d¹⁰ 4p⁴

Does Se have unpaired e-? How many?

2 unpaired e-

fill out the orbital notation and look at 4p

What does an s orbital look like?

looks like a circle

What does a p orbital look like?

looks like an 8

what does a d orbital look like?

looks like a 4 clover leaf or butterfly

Determine valence and core e- from… 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁴

6 valence e- , 28 core e-

whats the highest (outermost) number shell? n=4…. So 4s² and 4p⁴ 2+4=6

The rest is core e- so 28

Coulombs law equation

F= k_e (q₁q₂/r²)

F direct to q (doubling any q will double F)

F decreases ALOT as distance increases

common sense bro

atomic radius ___ when the # of e- shells ___

increases, increases