Don't know what you mean by "other half".  There is a $500 stimulus payment for dependents under the age of 17 who are claimed on your tax return. If you claimed such a dependent and have received a stimulus payment without the $500, you would have to contact the IRS to find out the reason. 

I'm also going through the same I only got 1200 and nothing for my son there no way to talk to anyone at the Irs. can someone lead me in the right direction? Please and Thank you

Your son must be under age 17 to qualify for the $500 payment..

He only 2 yrs old.

Did you file a tax return and claim your child on the return? Wait until the IRS online portal opens in a few days to see if there is a way to contact the IRS on the portal: https://www.irs.gov/coronavirus/economic-impact-payments

YES, SIR, I DID IT THROUGH YOU GUYS TURBO TAX.

I'm going through the same thing as well. Filled with turbo tax and claimed my 11 year old son got eic for him and my daughter was also on there for a dependent. Only got the $1200 for myself. Only thing I could find out was that those who have received a payment will get a letter from the IRS in 15 days and it will tell you what to do from there if you have not received a payment. 

https://www.irs.gov/coronavirus/economic-impact-payment-information-center
For security reasons, the IRS plans to mail a letter about the economic impact payment to the taxpayer’s last known address within 15 days after the payment is paid. The letter will provide information on how the payment was made and how to report any failure to receive the payment or the right amount of payment.

The stimulus check is actually an advance of a refundable tax credit for your 2020 tax return.  When you file your 2020 tax return your stimulus amount will be adjusted to provide you with the correct amount.