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Regarding the bonds in FesO₄, Fe and S have an ionic bond, while S and O have covalent bonds.
Elements form bonds to increase their stability. The main types of bonds are:
- Metallic bonds: they are formed between metals and the electrons are in a delocalized cloud.
- Ionic bonds: they are formed between metals (lose electrons) and nonmetals (gain electrons)
- Covalent bonds: they are formed between nonmetals, which share electrons.
Regarding the bonds in FesO₄:
- Fe is a metal and S a nonmetal, thus they will form ionic bonds.
- S and O are both nonmetals, thus they will form covalent bonds.
Regarding the bonds in FesO₄, Fe and S have an ionic bond, while S and O have covalent bonds.
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Answer: It takes 3.120 seconds for the concentration of A to decrease from 0.860 M to 0.260 M.
Explanation:
Integrated rate law for second order kinetics is given by:
k = rate constant = 
= initial concentration = 0.860 M
a= concentration left after time t = 0.260 M

Thus it takes 3.120 seconds for the concentration of A to decrease from 0.860 M to 0.260 M.
Answer:
Explanation:
a )
m = m₀ 
m is mass after time t . original mass is m₀ , λ is disintegration constant
λ = .693 / half life
= .693 / 1590
= .0004358
m = m₀ 
b )
m = 50 x 
= 40.21 mg .
c )
40 = 50 
.8 = 
= 1.25
.0004358 t = .22314
t = 512 years .
Answer:
C. fluorine (F) and chlorine (Cl)
D. arsenic (As) and antimony (Sb)
Explanation:
In the periodic table , all the elements are arranged according to the atomic number ,
and the elements are placed in groups and periods ,
The elements with similar chemical and physical properties are placed in a common group .
The elements present in the same group have the same number of valence electrons in the valence shell .
Hence , from the given options ,
fluorine (F) and chlorine (Cl) belongs to group 17 with 7 valence electrons in the outermost shell .
arsenic (As) and antimony (Sb) belong to group 15 with 3 valence electrons in the outermost shell .