S1-L3: The Periodic Table of Elements Flashcards
What is Atomic mass?
- single atom mass
- ->total mass of protons + neutrons + electrons
Define mass number (figure 1)
-total protons AND neutrons in nucleus
Outline what atomic number is (figure 1)
- also known as proton number
- identifies element
- n. of protons in nucleus
What is Dobereiner’s “Law of Triads”?
- 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
What was the 1864 British chemist, Newlands “Law of Octaves”? (figure 2)
- If chemical elements arranged according to increasing atomic weight
- ->those with similar physical AND chemical properties occur after each of 7 element interval
What did Mendeleev do with the periodic table and what did it show?
- arranged elements in increasing relative atomic mass order
- ->found chemical properties of elements AND their compounds showed periodic trend (pattern in table)
Describe the organisation of the modern periodic table including the following features:
- periods
- groups
- noble gases
(figure 3)
- 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
Outline and describe the “Periodic Law”
- 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
What are “families of elements”?
- elements which share certain characteristics
- ->in terms of observable behavior & atomic structure
State the common periodic table classifications
- Alkaline metals
- alkaline earth metals
- transition metals
- lanthanides
- Actinides
- Nobel gas
- non-metals
- metalloids
Describe Alkali metals
- Group 1
- silver coloured/ soft metals
- highly reactive AND rarely find in elemental form in nature
Give some examples of alkali metals
-lithium (Li)/ sodium (Na)/ Potassium (K)
Briefly explain what Alkaline Earth metals are
- Silver coloured/ soft metals
- group 2
- reactivity similar to alkali metals
State some examples of Alkaline Earth metals
-Beryllium (Be)/ Magnesium (Mg)/ Calcium (Ca)
Describe Nobel gases and give some examples
- group 18
- V. reactive AND toxic
- gases OR low boiling/ melting points
- non-metallic
- chemically inert
- like Ne/ Ar/ Kr/ Xe
- exist as atoms
What are metalloids?
- have metal and non-metal properties
- 6 elements belong to this family (diagonal from B)
Which 6 elements are the metalloids?
-Boron (B)/ Silicon (Si)/ Arsenic (As)/ Tellurium (Te)/ Astatine (At)/ Oganesson (Uuo)
Briefly explain and describe transition metals (D-Block) are
- 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
From the F-block of elements what are Lanthanides (including properties)?
- 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
State some examples of Lanthanides
-Lanthanum (La)/ Lutetium (Lu)
Explain what Actinides are (include properties)
- 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
Outline and describe non-metals
- 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
What are the general trends in properties of elements in the periodic table?
- 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
What happens to the size of an atom as you descend down a group?
-increases