Which of the following is an oxidation-reduction (redox) reaction?
A. Sr + F2 ->SrF2
B. Ag2S + AgNO3 → Ag2S + 2AgNO3
C. 2HCIO3 + Ba(OH)3 —> 2H2O + Ba(CIO3)2
D. Rb2CO3 + MgBr2 → 2RbBr + MgCO3

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If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom

Order of filling levels and sublevels of electrons: 1s²2s²2p⁶3s²3p⁶4s²3d¹⁰4p⁶5s²4d¹⁰5p⁶6s²3f¹⁴5d¹⁰6p⁶for an element with 5 electrons in the 3d energy level: full configuration: 1s²2s²2p⁶3s²3p³.