42
Mo
Molybdenum
95.95
Molybdenum
Transition metal
Molybdenum is element 42, symbol Mo. It sits in period 5, group 6, and weighs 95.95.
Metals filling an inner shell as they go, giving several oxidation states and colour.
- Atomic number
- 42
- Atomic weight
- 95.95
- Period
- Period 5
- Group
- Group 6
- Block
- d block
- Electron configuration
- [Kr] 5s2 4d4
- Neutrons
- 54
The periodic table
Rows are periods, columns are groups. Tap any square to open that element.
1H2He3Li4Be5B6C7N8O9F10Ne11Na12Mg13Al14Si15P16S17Cl18Ar19K20Ca21Sc22Ti23V24Cr25Mn26Fe27Co28Ni29Cu30Zn31Ga32Ge33As34Se35Br36Kr37Rb38Sr39Y40Zr41Nb42Mo43Tc44Ru45Rh46Pd47Ag48Cd49In50Sn51Sb52Te53I54Xe55Cs56Ba57La58Ce59Pr60Nd61Pm62Sm63Eu64Gd65Tb66Dy67Ho68Er69Tm70Yb71Lu72Hf73Ta74W75Re76Os77Ir78Pt79Au80Hg81Tl82Pb83Bi84Po85At86Rn87Fr88Ra89Ac90Th91Pa92U93Np94Pu95Am96Cm97Bk98Cf99Es100Fm101Md102No103Lr104Rf105Db106Sg107Bh108Hs109Mt110Ds111Rg112Cn113Nh114Fl115Mc116Lv117Ts118Og
Others in the same group
Neighbours by number
How to read this
- A row (period) is the number of electron shells. Elements in period 3 carry three of them.
- A column (group) tells you how many electrons sit in the outer shell — which is why a group behaves alike.
- Atomic weight runs at roughly twice the atomic number: about as many neutrons as protons.
- The 28 lanthanides and actinides are drawn below the table. Slotting them in would stretch it to 32 columns.
Frequently asked questions
Q. What are Molybdenum's number and symbol?
Element 42, symbol Mo, atomic weight 95.95.
Q. Where does it sit in the table?
Period 5, group 6 — a transition metal.
Q. What is its electron configuration?
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d4, or [Kr] 5s2 4d4 for short.
Q. How many neutrons does it have?
Rounding the atomic weight and subtracting the atomic number gives 54. The exact count depends on the isotope.