Atomic Structure. Subatomic Particles (Particles that make up an atom) ● Proton (p+) - Positively...
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Transcript of Atomic Structure. Subatomic Particles (Particles that make up an atom) ● Proton (p+) - Positively...
Subatomic ParticlesSubatomic Particles(Particles that make up an atom)(Particles that make up an atom)
● ● Proton (p+)Proton (p+)- Positively charged - Positively charged - Found in the nucleus- Found in the nucleus- Large mass- Large mass
●● Neutron (nNeutron (n00))- A neutral particle - A neutral particle - Found in the nucleus- Found in the nucleus- Large mass- Large mass
●● Electron (e-)Electron (e-)- Negatively charged particle - Negatively charged particle - Found outside of the nucleus in the electron - Found outside of the nucleus in the electron
cloudcloud- Very small mass- Very small mass
SummarySummary
●● The nucleus has almost all of the mass & it The nucleus has almost all of the mass & it has a + chargehas a + charge●● The electron cloud has a – charge & The electron cloud has a – charge & creates the atom’s creates the atom’s volumevolume
How to read a box on the How to read a box on the periodic tableperiodic table
11
Na 22.98
● Atomic Number - # above symbol
- Always determines # of protons (can never change!)
- Determines # of electrons if atom is neutral (0 charge)
- We assume the periodic table is neutral (same # of p+ & e-)
● Summary:
- Sodium’s atomic number is 11
- Sodium has 11 protons & 11 electrons
Atomic #Symbol
11
Na
22.98● Average atomic mass - # below the symbol in decimal form
- The average mass of an atom
- Not all sodiums have the same mass due to different number of neutrons (isotope)
Average atomic mass
● Mass Number – rounding the a.a.m. to a whole number
- Mass # = # of protons + number of neutrons
- Therefore, use to find number of neutrons mass # - # of p = # of n
● Summary- Na’s ave. atomic mass = 22.98 amu
(atomic mass units)- Na’s mass # = 23- Number of neutrons in Na:
23 – 11 = 12 neutrons
11
Na
22.98
Mass #
(23)
You just have to try one!You just have to try one!
47
Ag 107.87
Determine:
1. Atomic # =
2. # of protons =
3. # of electrons =
4. Ave. atomic mass =
5. Mass number =
6. # of neutrons =
IsotopesIsotopes● Atoms of the same element can have different numbers of neutrons, therefore, different masses
- Remember, neutrons have mass!
- Changing the number of neutrons, changes the mass
● Let’s look at 2 isotopes of carbon as an example:
- Carbon ALWAYS has 6 protons
- But it can have a mass of 12 amu
(6p + 6n) C or C-12
- and it can have a mass of 14 amu
(6p + 8n) C or C-14
12
14
6
6
Perfect practice makes Perfect practice makes perfect!perfect!
● Here is an isotope of oxygen: O- How many protons are present? __________
- What is the mass number? __________
- How many neutrons are present? __________
- How many electrons are present? __________
● Write the shorthand form of a nitrogen isotope that has 13 neutrons.
_ N or N - __
188
_
Mole ConversionsMole Conversions● Moles (mol) are a unit of measurement
● 1 mole = 6.02 x 1023 units (atoms, molecules, formula units,
ions, etc)
● 6.02 x 1023 is Avogadro’s number
● Mole Conversions
1 mole = 6.02 x 1023 units = formula weight (grams)
What is formula weight?What is formula weight?
● Formula weight is the weight of an element or compound in grams
● How is formula weight determined?
- Use your periodic table and find the ave. atomic mass
- Formula weight of H2O
- H’s ave. atomic mass = 1.01 g (x 2) = 2.02 g
- O’s ave. atomic mass = 16.00 g
2.02 g + 16.00 g = 18.02 g H18.02 g H22OO
What is the formula What is the formula weight of…weight of…
AlAl BrBr22
MgFMgF22
CHCH44
CaCa33(AsO(AsO44))22
ConversionsConversions1. Moles to grams
# of moles x formula weight (g) = _____ grams 1 1 mole
● Example: How many grams are in 5.00 moles of CaCl2?
Formula weight of CaCl2:
● Ca = 40.08 g Cl = 35.45 g (x2) = 70.90 g
● 40.08 g + 70.90 g = 110.98 g CaCl2
5.00 moles x 110.98 g CaCl2 = 554.9 = 1 1 mole
555 g CaCl2
2. Grams to moles
# of grams x ___1 mole _ = _______ moles 1 formula wt (g)
● Example: How many moles are in 25.00 g of NaCl?
25.00 g of NaCl x _ 1 mole___ = 1 58.44 g NaCl
0.4278 moles of NaCl
3. Moles to units (atoms, molecules, formula units, ions, etc.)
# of moles x 6.02 x 1023 units = ____ units1 1 mole
● Example: How many atoms are in 0.250 moles of neon?
0.250 moles of Ne x 6.02 x 1023 atoms = 1 1 mole1.51 x 1023 atoms
of Ne
4. Units to moles
# of units x ___1 mole____ = ____ moles 1 6.02 x 1023 units
● Example: How many moles are in 4.23 x 1024 molecules of H2O?
4.23 x 1024 molecules x ______1 mole______ = 1 6.02 x 1023 molecules
7.03 moles of H2O
5. Grams to units
# of grams x 6.02 x 1023 units = ____ units 1 formula wt (g)
● Example: How many formula units are in 35.0 g of K2O?
35.0 g K2O x 6.02 x 1023 formula units = 1 94.20 g
K2O 2.24 x 1023 formula units of K2O
6. Units to grams
# of units x _formula wt (g)_ = ____ grams 1 6.02 x 1023 units
● Example: How many grams are in 9.75 x 1025 atoms of Ag?
9.75 x 1025 atoms x __107.87 g Ag__ = 1 6.02 x 1023
atoms
17500 g Ag
Mass Percent CompositionMass Percent Composition● Determining what percentage of each element is in a specific formula
● Example: Find the mass % of each element in NaHCO3.
- Step 1: Find their individual ave. atomic masses from the PT & multiply by the number of atoms of each (subscript)
Na = 22.99 g (1) = 22.99 g H = 1.01 g (1) = 1.01 gC = 12.01 g (1) = 12.01 gO = 16.00 g (3) = 48.00 g
84.01 g NaHCO3
- Step 2: Add them to get the total weight of the formula.
- Step 3: Find the mass % of each!
-Remember: Na = 22.99 g (1) = 22.99 g H = 1.01 g (1) = 1.01 gC = 12.01 g (1) = 12.01 gO = 16.00 g (3) = 48.00 g
84.01 g of NaHCO3
- Take the elements individual total weight and divide by the total weight of the formula. Then Multiply by 100.
- Mass % of Na = 22.99g /84.01 (100) = 27.36 %
- Mass % of H = 1.01g /84.01 (100) = 1.20 %
- Mass % of C = 12.01g /84.01 (100) = 14.30 %
- Mass % of O = 48.00g /84.01 (100) = 57.14 %
- Add %’s to make sure they add up to 100%
Getting the formula from Getting the formula from mass %mass %
● Do the opposite of finding the mass %
● Example: What is the formula of a substance that is made of 27.29% C & 72.71% O. The total weight of the substance is 44.01 g.
- Step 1: Divide each % by 100 then multiply by the total weight
C : 27.29/100 = 0.2729 (44.01 g) = 12.01 g C
O: 72.71/100 = 0.7271 (44.01 g) = 32.00 g O
- Step 2: Divide the totals by their average atomic mass (from PT)
12.01 g C/12.01 g C = 1
32.00 g O/16.00 g O = 2
- Step 3: Put the formula together
CO2
Finding the relative Finding the relative atomic massatomic mass
● Where does the periodic table get its average atomic masses from?
● Here’s an example:
There are two isotopes of chlorine which consists of atoms of relative isotopic masses 35.0 (75.0 %) and 37.0 (25.0 %).
% abundance Isotope mass
Cl-35 75.0 35.0 amu
Cl-37 25.0 37.0 amu
(75.0/100) x 35.0 amu + (25.0/100) x 37.0 amu =
35.5 amu
The answer matches Cl on the periodic table!