A. Sodium is correct. 
Sodium is an alkali metal. 
Aluminum is a post-transitional metal- still a metal but it’s character is not as metallic as sodium. 
Silicon is a metalloid- it has characteristics from both the metals and the non-metals. 
Phosphorous is a non-metal.
        
             
        
        
        
The pH of normal rainwater is 5.6. It's slightly acidic
        
                    
             
        
        
        
Answer:
C.) Argon
Explanation:
This is because ionisation energy increases as we move from left to right in a period. Argon presents in the right most column and Argon is a novel gas and has 8 electrons in outermost orbital. So, it is highly stable. I hope I helped! ^-^
 
        
             
        
        
        
A because cation is positive and anion is negative evening it out at constant.
        
             
        
        
        
Answer: 
The number of molecules is 1.4140*10^24 molecules 
Explanation:
To know the number of molecules, we need to determine how many moles of water we have, water has molar mass of 18.015g/mol
This means that one mole of water molecules has a mass of 18.015g.
42.3g * 1 mole H2O/18.015g
= 2.3480 moles H2O
We are using avogadros number to find the number of molecules of water
2.3480 H2O * 6.022*10^ 23moles/ 1mole of H2O
That's 2.3480 multiplied by 6.022*10^23 divided by 1 mole of H2O
Number of molecules = 1.4140 *10^24 molecules