H -->+1
He --> 0
Be -->
B
The oxidation number of V in V2O7-4 is +5, since the overall charge of the ion 4- is balanced by two vanadium atoms with an oxidation state of +5 each. The oxidation number of O is -2, as it typically has a -2 charge in compounds.
The oxidation number of calcium in calcium fluoride (CaF2) is +2, because calcium typically forms ions with a charge of +2. The oxidation number of fluorine in CaF2 is -1, because fluorine usually has a charge of -1.
The mass numbers of the first 20 elements from hydrogen (1) to calcium (20) are as follows: 1 (H), 4 (He), 7 (Li), 9 (Be), 11 (B), 12 (C), 14 (N), 16 (O), 19 (F), 20 (Ne), 23 (Na), 24 (Mg), 27 (Al), 28 (Si), 31 (P), 32 (S), 35 (Cl), 40 (K), 39 (Ca).
Regarding the oxidation states of the atoms in the tetrathionate ion: The tetrathionate polyatomic ion is made of four sulfur atoms, each with an oxidation number of +1, and six oxygen atoms each with an oxidation number of -1. Note, this is one of the rare exceptions to the 'rule' that oxygen normally has a minus two oxidation number. Other -1 oxygen compounds are the peroxides. An interesting half reaction is the oxidation of two thiosulfate ions to tetrathionate, in which sulfur has an oxidation number of +2 in the reactant and +1 in the product. Oxygen has an oxidation number of -2 in the reactant, and -1 in the product. 2S2O3-2 ----> S4O6-2 + 2 e-
21 --- Elements with the atomic number between 98 and 118; other elements as Pm, Tc, Pu, Np, Cm, Am, Bk were first obtained in laboratory and only after they were discovered in nature in extremely low traces.
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The oxidation number of V in V2O7-4 is +5, since the overall charge of the ion 4- is balanced by two vanadium atoms with an oxidation state of +5 each. The oxidation number of O is -2, as it typically has a -2 charge in compounds.
Approx. 20 elements were known in 1800.
The oxidation number of calcium in calcium fluoride (CaF2) is +2, because calcium typically forms ions with a charge of +2. The oxidation number of fluorine in CaF2 is -1, because fluorine usually has a charge of -1.
The mass numbers of the first 20 elements from hydrogen (1) to calcium (20) are as follows: 1 (H), 4 (He), 7 (Li), 9 (Be), 11 (B), 12 (C), 14 (N), 16 (O), 19 (F), 20 (Ne), 23 (Na), 24 (Mg), 27 (Al), 28 (Si), 31 (P), 32 (S), 35 (Cl), 40 (K), 39 (Ca).
HydrogenHeliumLithiumBerylliumBoronCarbonNitrogenOxygenFluorineNeonSodiumMagnesiumAluminumSiliconPhosphorousSulphurChlorineArgonPotassiumCalciumHope this helped :)
Regarding the oxidation states of the atoms in the tetrathionate ion: The tetrathionate polyatomic ion is made of four sulfur atoms, each with an oxidation number of +1, and six oxygen atoms each with an oxidation number of -1. Note, this is one of the rare exceptions to the 'rule' that oxygen normally has a minus two oxidation number. Other -1 oxygen compounds are the peroxides. An interesting half reaction is the oxidation of two thiosulfate ions to tetrathionate, in which sulfur has an oxidation number of +2 in the reactant and +1 in the product. Oxygen has an oxidation number of -2 in the reactant, and -1 in the product. 2S2O3-2 ----> S4O6-2 + 2 e-
Period 1 (Elements 1 and 2)1s1 - 1s2Period 2 (Elements 3 - 10)2s1 - 2s22p6Period 3 (Elements 11 - 18)3s1 - 3s23p6Period 4 (Elements 19 and 20)4s1 - 4s2
21 --- Elements with the atomic number between 98 and 118; other elements as Pm, Tc, Pu, Np, Cm, Am, Bk were first obtained in laboratory and only after they were discovered in nature in extremely low traces.
It is simply that among period 2 elements, oxygen (8) is one of the elements which has the largest number of isotopes, among period 4 elements, calcium (20) has the largest number of isotopes, and among period 5 elements, tin (50) has the largest number of isotopes. In fact tin has the largest number of isotopes overall.
The first prime after 20 is 23.
2 power 20