Answer:
francium
Explanation:
the atomic radius increases from top to bottom in a group, and decreases from left to right across a period.
 
        
             
        
        
        
Answer:
A: element B
B: element A
C: element B
D: element A
Explanation:
decrease in size leads increase in electronegativity because the smaller the size, the closer the shell is to the nucleus. Also, atomic radius decreases to the right and up on the periodic table. Atomic radius increases to the left and down a period. I hope this helps!
 
        
             
        
        
        
If the temperature rises in a reaction. Exothermic is if it loses heat. 
Have a nice day, brainliest would be fantastic.
        
             
        
        
        
Potassium oxide: K₂O.
There's no need for prefixes since K₂O is an ionic compound.
<h3>Explanation</h3>
Find the two elements on a periodic table:
- Potassium- K- on the left end of period four.
 - Oxygen- O- near the right end of periodic two.
 
Elements on the bottom-left corner of the periodic table are metals. Those on the top-right corner are nonmetals. 
- Potassium is a metal,
 - Oxygen is a nonmetal.
 
A metal and a nonmetal combine to form an ionic compound. Potassium oxide is likely to be an ionic compound. It contains two types of ions: 
- Potassium ions: Potassium is group 1 of the periodic table. It is an alkaline metal. Like other alkaline metals such as sodium Na, potassium K tends to lose one electron and form ions of charge +1 in compounds. The ion would be K⁺.
 
- Oxide ions from oxygen: Oxygen is the second most electronegative element on the periodic table. It tends to gain two electrons and form the oxide ion 
 when it combines with metals.  
The two types of ions carry opposite charges. They shall pair up at a certain ratio such that they balance the charge on each other. The charge on each 
 ion is twice that on a 
 ion. Each 
 would pair up with two 
. Hence the subscript in the formula: 
.
There are two classes of compounds:
- Covalent compounds, which need prefixes, and
 - Ionic compounds, which need no prefix.
 
Prefixes are needed only in covalent compounds. For instance in the covalent compound carbon dioxide 
, the prefix di- indicates that there are two oxygen atoms in the formula 
. However, there's no need for prefix in ionic compounds such as 
.
 
        
             
        
        
        
Answer: 1+
Justification:
The ionization energies tell the amount of energy needed to release an electron and form a ion. The first ionization energy if to loose one electron and form the ion with oxidation state 1+, the second ionization energy is the energy to loose a second electron and form the ion with oxidation state 2+, the third ionization energy is the energy to loose a third electron and form the ion with oxidation state 3+.
The low first ionization energy of element 2 shows it will lose an electron relatively easily to form the ion with oxidations state 1+.
The relatively high second ionization energy (and third too) shows that it is very difficult for this atom to loose a second electron, so it will not form an ions with oxidation state 2+. Furthermore, given the relatively high second and third ionization energies, you should think that the oxidation states 2+ and 3+ for element 2 never occurs.
Therefore, the expected oxidation state for the most common ion of element 2 is 1+.