1) Nuclear reactions involve a change in an atom's nucleus, usually producing a different element. Chemical reactions, on the other hand, involve only a rearrangement of electrons and do not involve changes in the nuclei. ... (3) Rates of chemical reactions are influenced by temperature and catalysts.
Answer:
24.5 g of NaCl
Explanation:
We begin from the balanced reaction:
3MgCl₂ + 2Na₃PO₄ → 6NaCl + Mg₃(PO₄)₂
If the sodium phosphate is in excess, then the limting reagent is the magnessium chloride.
We convert mass to moles:
20 g . 1mol / 95.2g = 0.210 moles.
3 moles of MgCl₂ can produce 6 moles of NaCl
0.210 moles of salt, may produce (0.210 . 6) /3 = 0.420 moles
Ratio of reactant is twice the product
We convert the moles to mass:
0.420 mol . 58.45 g/mol = 24.5 g
Answer:
has 4 electrons in its valence shell.
Explanation:
Silicon has 14 protons, so its neutral atom has also 14 electrons, thus, the electron distribution following the Linus Pauling's diagram is:
1s² 2s²2p⁶ 3s²3p²
Thus, it has 4 electrons in its valence shell (3), likely carbon. So, silicon would have some of the properties of carbon, such as form 4 bonds, and the structure would be similar.
Answer: 1. C. polar covalent: electrons shared between silicon and sulfur but attracted more to the sulfur
2. B) 
3. B) Fluorine
Explanation:
1. A polar covalent bond is defined as the bond which is formed when there is a difference of electronegativities between the atoms.
Electronegativity difference = electronegativity of sulphur- electronegativity of silicon = 2.5 -1.8 = 0.7
Thus as electronegativity difference is less than 1.7 , the cond is polar covalent and as electronegativity of sulphur is more , the electrons will be more towards sulphur.
2. A molecular compound is usually composed of two or more nonmetal elements. Example:
Ionic compound is formed by the transfer of electrons from metals to non metals. Example:
,
and 
3. For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.
Here K is having an oxidation state of +1 and as the compound formed is KZ, the oxidation state of non metallic element Z should be -1. Thus the element Z is flourine which exists as diatomic gas 
The Eukaryotic cell has a nucleus