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CHEMISTRY-FY > S1-L3: The Periodic Table of Elements > Flashcards

S1-L3: The Periodic Table of Elements Flashcards

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1
Q

What is Atomic mass?

A
  • single atom mass

- ->total mass of protons + neutrons + electrons

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2
Q

Define mass number (figure 1)

A

-total protons AND neutrons in nucleus

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3
Q

Outline what atomic number is (figure 1)

A
  • also known as proton number
  • identifies element
  • n. of protons in nucleus
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4
Q

What is Dobereiner’s “Law of Triads”?

A
  • Arithmetic mean of atomic masses of 1st AND 3rd element in triad approx equal to 2nd elements atomic mass in that triad
  • examples: Cl/Br/I–> weight 35.5/ 80/ 127
  • 1817 scientist
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5
Q

What was the 1864 British chemist, Newlands “Law of Octaves”? (figure 2)

A
  • If chemical elements arranged according to increasing atomic weight
  • ->those with similar physical AND chemical properties occur after each of 7 element interval
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6
Q

What did Mendeleev do with the periodic table and what did it show?

A
  • arranged elements in increasing relative atomic mass order

- ->found chemical properties of elements AND their compounds showed periodic trend (pattern in table)

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7
Q

Describe the organisation of the modern periodic table including the following features:

  • periods
  • groups
  • noble gases

(figure 3)

A
  • elements arranged in increasing order of atomic number (Z) from left to right across table
  • Periods: horizontal rows
  • groups: vertical columns
  • noble gases: found right side of periodic table
  • progression runs from metals to non-metals across each period
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8
Q

Outline and describe the “Periodic Law”

A
  • formal statement: properties of elements are periodic functions of their atomic numbers
  • ->when elements arranged in increasing atomic number there is periodic pattern in their physical AND chemical properties
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9
Q

What are “families of elements”?

A
  • elements which share certain characteristics

- ->in terms of observable behavior & atomic structure

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10
Q

State the common periodic table classifications

A
  • Alkaline metals
  • alkaline earth metals
  • transition metals
  • lanthanides
  • Actinides
  • Nobel gas
  • non-metals
  • metalloids
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11
Q

Describe Alkali metals

A
  • Group 1
  • silver coloured/ soft metals
  • highly reactive AND rarely find in elemental form in nature
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12
Q

Give some examples of alkali metals

A

-lithium (Li)/ sodium (Na)/ Potassium (K)

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13
Q

Briefly explain what Alkaline Earth metals are

A
  • Silver coloured/ soft metals
  • group 2
  • reactivity similar to alkali metals
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14
Q

State some examples of Alkaline Earth metals

A

-Beryllium (Be)/ Magnesium (Mg)/ Calcium (Ca)

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15
Q

Describe Nobel gases and give some examples

A
  • group 18
  • V. reactive AND toxic
  • gases OR low boiling/ melting points
  • non-metallic
  • chemically inert
  • like Ne/ Ar/ Kr/ Xe
  • exist as atoms
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16
Q

What are metalloids?

A
  • have metal and non-metal properties

- 6 elements belong to this family (diagonal from B)

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17
Q

Which 6 elements are the metalloids?

A

-Boron (B)/ Silicon (Si)/ Arsenic (As)/ Tellurium (Te)/ Astatine (At)/ Oganesson (Uuo)

18
Q

Briefly explain and describe transition metals (D-Block) are

A
  • elements with at least one oxidation state
  • -> has partially filled d-subshell
  • metal melting/ boiling points AND high densities
  • form coloured compounds AND complex ions (dissolved in water)
  • valencies variable PLUS ions readily undergo oxidation/ reduction
  • -> E.G: Fe2+ + e- –> Fe3+
  • able to use e-‘s from outer two orbitals for combination with other elements
19
Q

From the F-block of elements what are Lanthanides (including properties)?

A
  • 15 elements with atomic number 57-71
  • also known as rare earth metals
  • shiny & silvery white
  • easily stain when exposed to air
  • high m/ b points
20
Q

State some examples of Lanthanides

A

-Lanthanum (La)/ Lutetium (Lu)

21
Q

Explain what Actinides are (include properties)

A
  • 15 elements with atomic numbers 89-103
  • v. dense metals with distinctive structures
  • numerous allotropes
  • -> plutonium has minimum 6 allotropes
  • combine directly with most non-metals
22
Q

Outline and describe non-metals

A
  • Groups 14-16
  • cant conduct electricity/heat well
  • v brittle unlike metals ALSO cant roll in to wires/pound in to sheets
  • exist as two/three states of matter at room temp- gases (O2) AND solids (C)
  • no metallic sheen/ glow AND not reflect light
23
Q

What are the general trends in properties of elements in the periodic table?

A
  • all elements of given group have V. similar physical + chemical properties
  • ->with regular graduation in properties moving top to bottom of group
  • -> can also see patterns going across a period
24
Q

What happens to the size of an atom as you descend down a group?

A

-increases

25
Q

Outline the trend in metallic character in the periodic table

A
  • increases moving top to bottom in group
  • apparent in groups IVA/ VA & VIA
  • begins with non-metals (C/N/O) and ends with metals (Pb/ Bi and Po)
26
Q

What happens to reactivity down a group?

A
  • metals more reactive descending group

- non-metals become less reactive down group too

27
Q

Describe electron shells in terms of the periodic table (figure 4)

A
  • n. of shells equal to period number to which element belongs to such as group 1
  • going down group n. of e- shells increases by 1 each time
28
Q

What is Valency?

A

-N. of chemical bonds formed by atom

29
Q

Give the IUPAC definition of valency

A

-max n. of univalent atoms (like H) which may combine with atom of element under consideration/ with fragments/ for which atom of this element may be substituted

30
Q

What is monatomic ion valency equal to and state some examples?

A
  • equal to it’s charge
  • (H+) valency is 1/ (O2-) valency is 2/ (K+) valency is 1/ (Al 3+) valency is 3
  • some elements may have multiple valencies
  • ->like phosphorus (P)/ Nitrogen (N)- valency is 3/5
  • transition metals
31
Q

What happens to the number of valence e-‘s down a group?

A

-N. of e-‘s in outer shell of atom unchanged

32
Q

Outline what the valency of elements is equal to in relation to their group number

A
  • groups I/III/IV –> valency equal to group number

- groups IV/ V/ VI/ VII/ VIII –> valency equal to (8 - group number)

33
Q

State the steps which must be followed to write the formula of chemical compound using the examples of

Na2SO4 and CH4

A

1- write symbols for elements & ions: Na(SO4)/ C/ H
2- write valency above AND right of symbols: Na^+1 (SO4)^2- / C^4 / H^1
3- identify how many of each atom needed to make n. of bonds needed by each atom/ ion
–>write numbers to right and below of symbol
–>trick: reverse valencies

–> Na2SO4 AND CH4

34
Q

Calculate the molecular mass of Calcium Carbonate; CaCO3

Ca=40/ C=12/ O=16

A
  • so CaCO3

- -> 40 + 12 + 3(16)= 100

35
Q

Define Empirical formula and give some examples

A
  • expresses elemental composition of compound as ratio

- ->examples: water (HO)/ Hydrogen Peroxide (HO)/ Glucose (CH2O)

36
Q

What is Molecular formula?

A

-exact n. of each atom type present in one molecule of compound

37
Q

State some examples of molecular formula

A

-water (H2O)/ hydrogen peroxide (H2O2)/ Glucose (C6H12O6)

38
Q

How can you calculate the empirical formula from experimental results? Use the following example:

Compound contains: 32.4% Na/ 22.5% S/ 45.1% O by mass. Calculate it’s empirical formula

A

1- Mass% (assuming 100g): Na= 32.4/ S= 22.5/ O= 45.1
2-relative n. of atoms (% mass/Ar): 32.4/23= 1.41
–>22.5/32= 0.7
–>45.1/16= 2.82
3- Divide by smallest number: 1.41/0.7= 2
–>0.7/0.7= 1
–> 2.82/0.7= 4
–>so empirical formula is Na2SO4

39
Q

Use the answer from the same example previously to calculate the molecular formula of the compound

A
  • RMM of this compound is 142 so molecular formulae
  • -> empirical formula mass= (2x23) + 32 + (4x16)= 142
  • ->RMM/142= 1
  • ->therefore formula is Na2SO4
40
Q

Calculation of % composition from a formula

Example: Formula of crystal ferrous sulphate is FeSO4.7H2O. What is the % of iron by mass in ferrous sulphate?

A
  • 56 + 32 + (4x16) + 7x (2x1 + 16)= 278
  • ->56 parts iron in 278 parts of compound
  • ->so % of iron by mass:
    (56x100) / 278 = 20.1%
41
Q

Summary of lecture

A
  • Periodic table: elements ordered by atomic number/ electronic structure
  • can use to predict chemical AND physical of elements like reactivity/ valency
  • write formula of compound using valency:
  • ->calculate % mass of each element in compound from chemical formula
  • ->calculate empirical AND molecular formulae of compound from its % mass composition

CHEMISTRY-FY (11 decks)

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