All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
There are two conditions for the Zakat to be obligatory about money or gold:
1) They should reach the minimum amount liable for Zakat, which is what is of the same value of 85 grams of gold.
2) One whole lunar year should elapse.
So whoever has 85 grams of gold or more, or has an amount of money that is equal to the value of 85 grams of gold or more, and a whole year elapses, then it is an obligation to pay 2.5% Zakat from them. So if you have 120 grams of gold and a complete year elapses since you possessed it, and you possess other money and a whole year elapses on them, then you have to add the value of gold to the amount of money that you possess and pay 2.5% Zakat. As regards whether you should add your money to the money of your wife and then pay Zakat, the answer is no. But each one of you should pay the Zakat for his own wealth, if it reaches the minimum amount liable for Zakat and a complete year elapses since their possession, then 2.5% Zakat has to be paid. Then there is no harm after that to combine the amount of Zakat from your wealth and your wife's wealth and give it to the people who are entitled for Zakat, and this is detailed in Fatwa: 88368 and 86546.
Allaah knows best.