Classification and Periodicity of Elements Flashcards
(59 cards)
Nomenclature of IUPAC elements, give basis:
0 nil n
1 un u
2 bi b
3 tri t
4 quad q
5 pent p
6 hex h
7 sept s
8 oct o
9 enn e
Names are assigned with respective words for numbers and suffix ium
Symbol consists of three letters for each word, first being capital.
Ex: Element with atomic no.120
Ans: Ubn - unbinilium
Name all Groups in the modern PT.
G1: Alkali Metals
G2: Alkaline Earth Metals
G3-G12: Transition Elements
G13: Boron Family
G14: Carbon Family
G15: Nitrogen Family
G16: Oxygen Family/Chalcogens
G17: Halogens
G18: Inert Gases
How many elements are known at present?
118 elements
Explain Dobereiner’s Triads
Dobereiner noted similarities in physical and chemical properties of elements in groups of three and called them Triads. In each case, the middle element had an atomic weight half way between the atomic weights of other two and properties between the other two. This was known as Law of Triads.
Many elements couldn’t fit in this system of classification and were left out, especially elements with very low or high mass elements.
How did Lavoiser classify arrangement of elements.
He did not introduce metalloids and simply divided the known 33 elements into metals and non-metals.
Explain Newland’s Law of Ocatves?
Newland noticed that when elements were arranged by the atomic weights, every first and eighth element had similar properties.
This later proved to be only true upto calcium.
Write notes on Mendeleev’e Periodic Law/Table
Working independently, two scientists Meyer and Mendeleev suggested that arranging elements in order of their increasing atomic weights resulted in repeating similar physical and chemical properties at regular intervals. Meyer plotted a graph for such properties and noticed a periodicity pattern.
Later, Mendeleev gave the Periodic Law which states:
“The properties of the elements are a periodic function of their atomic weights”.
Mendeleev arranged elements in horizontal rows and vertical columns in such a way that elements with similar properties occupied the same column and group.
His greatest work was when he left several gaps in the table initiating that some of the elements were still undiscovered to be put there.
He left gaps under Silicon and Aluminium and called the Eka-Silicon and Eka-Aluminium respectively. These later came to be known as Germanium and Gallium.
How did Modern Periodic Law came to be?
After discovery of sub-atomic particles, Henry Moseley observed regularities in the characteristics of X-Ray spectra of elements. He plotted the the graph of √v (√freq) against atomic number(z) and noticed it resulted in a straight line and not the graph of √v and atomic weight.
Therefore, he concluded that atomic number is a more fundamental property of elements.
He then modified Mendeleev’s Periodic Law and named it Modern Periodic Law:
“The physical and chemical properties of elements are a periodic function of their atomic numbers”.
What causes the periodicity in physical and chemical properties of elements?
The periodic variance in electronic configuration.
Or, repetition in similar electronic configuration of outer energy levels.
Tell characteristics of Periods and Groups?
There are 7 Periods, seventh of which is incomplete as of today and 18 groups.
Periods corresponds to highest principal quantum number (n) and tells us about shell.
Groups tell us about electron valence.
The first period contains 2 elements and then 8,8,18,18,32.
14 elements of both 6th and 7th period are listed seperately in f-block and are called Lanthanoids and Actinoids.
Explain Lanthanoids and Actanoids.
Also known as transition elements, they are 14 elements of the 6th and 7th period that are separated into the f-block.
They have been placed separately in the periodic table because of their electronic configurations (them filling their 4f electron shell), properties (different from PT elements), and convenience for keeping the periodic table organized.
Lanthanoids are elements 58–71; also known as rare-earth elements. They are known for being difficult to synthesize and are less reactive than actinoids. They have a maximum oxidation state of +4 and are mostly silver active metals with strong reducing ability.
Actinoids are elements 90–103;
they are all radioactive and most are not naturally found on Earth. They are closely related to nuclear chemistry and nuclear energy. They have an oxidation state ranging from +2 to +7
Share some similarities/differences between Lanthanoids and Actinoids.
Both groups have elements mostly in the +3 oxidation state.
Both groups have partially filled f-orbitals.
Lanthanoids have 4f series elements, while actinoids have 5f series elements.
Lanthanoids are non-radioactive, except for Promethium.
Define Bridge Elements.
Bridge elements are elements in the second period of the periodic table that have similar properties to elements in the third period. They do so in a diagonal relationship.
Ex:
Li - Mg
Be - Al
B - Si
What is electronic configuration?
Distribution of electrons into orbitals of an atom is called it’s electronic configuration.
Principal Quantum no. (n) defines main energy level known as shell. An elements location in PT reflects the (n) of last orbital filled.
The number of elements present in a period is twice _________________?
The number of atomic orbitals available in the energy level that is being filled.
Which period consists of mostly man-made radioactive elements?
7th Period
Which series is called inner transition series?
4f series (Lanthanoids) and 5f series (Actinoids)
Write short note on S-Block
Consists of G1(Alkali Metals) and G2(Alkaline Earth Metals) and are all reactive metals with low ionisation enthalpies, exceptions are H and He.
Have electronic configuration ns¹ and ns².
General: ns¹-²
Lose outermost electrons to form 1+ ion (G1) and 2+ ion (G2).
The metallic character and reactivity increases as we go down the group. Because of high reactivity, never found pure in nature.
Write short note on P-Block.
Consists of G13 to G18. Mostly non-metals. Form covalent compounds. Form acidic oxides and generally have no colors to flame.
Contain Halogens (G17) and Chalcogens (G16). These two groups have very high negative electron gain enthalpies, as they only need one (G17) or two (G18) electrons to achieve stable configuration.
Have electronic configuration of ns²np¹ to ns²np⁶.
General: ns²np¹-⁶
At each period’s end (G18 element) is a noble gas with valence shell ns²np⁶ configuration. This is why (fully filled configaration) noble gases possess very low chem. reactivity.
The non-metallic character increases as we go from left to right.
Write short note on D-Block.
Also known as transition elements (form bridge between chem. active and less active elements of s and p-block). Consist of (G3) to (G12). Characterised by filling of inner d-orbitals. They are all metals.
High-melting points, density, large atomic/ionic radii. paramagnetic (often used as catalysts), form color ions and compounds.
Have general electronic configuration of: (n-1)d¹-¹⁰ns⁰-²
Exception: Pd (4d¹⁰5s⁰)
Zn, Cd and Hg do not show most properties of Transition elements.
Write short note on F-Block.
Also known as inner-transition elements as they contain Lanthanoids(58-71) and Actinoids(90-103). Characterised by last electron being filled in f-orbital. They are all metals (heavy metals). Form complex compounds.
Have general electronic configuration of: (n-2)f¹-¹⁴(n-1)d⁰-¹ns²
All Actinoids are radioactive elements. Lanthanoids are non-radioactive with exception of Pm(Promethium).
Elements after (U)ranium(92) are called Transuranium elements
Write short note on metals.
Metals compromise more than 78% of elements we know, and appear mostly on the left side of PT.
They’re usually solids at room temp with exception of mercury. They usually have high melting and boiling points, exceptions being Gallium and Caesium. They are good conductor of heat and electricity. Malleable and Ductile. Generally sonorous.
As we go down a group, valence electron gets farther away from nucleus, meaning it is taken away from atom more easily, more metallic character (gives away electron easily). Therefore, electron losing tendency also increases, meaning metallic character also increases.
Write short note on Non-Metals.
Generally located at top right side of PT. So we conclude that metallic character decreases along a period.
They’re usually solids or gases at room temp with low melting and boiling points, exceptions being Boron and Carbon. Poor conductors of heat and electricity.
Generally brittle, neither ductile not malleable, not sonorous.
Elements become more non-metallic as we go from right to left a period.
What are Metalloids?
Elements running a diagonal line across PT that show both the properties of metals and non-metals are known as either Semi-metals of Metalloids.
Ex: Arsenic, Germanium, Silicon, Antimony and Tellurium.
