Nitrogen
Explanation:
Adding one proton to a carbon atom makes Nitrogen. 
 A quick introspection on atoms: 
- An atom is made up of three fundamental particles. 
- They are protons, neutrons and electrons. 
- The protons are positively charged and the neutrons do not carry any charges.
- Electrons are negatively charged. 
The difference between an atom and another is the number of protons in them. This is the atomic number. 
The periodic table of element is a list of elements arranged based on the number of protons they have. Every element on the table has unique number of protons which makes it differ from another. 
- Atoms do not readily lose their protons because they are held by nuclear forces in the nucleus of an atom. 
When an element gains a proton, it becomes another element. 
     Carbon has proton number of 6
  If a proton is added to it, it becomes 7
This is the proton or atomic number of nitrogen. 
Learn more: 
Atomic number brainly.com/question/5425825
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