Which factor causes helium to have a higher first ionisation energy than hydrogen?

1.3.1.1 shells, sub-shells and orbitals

1.3.1.2 principal quantum number (n)

1.3.1.3 ground state, limited to electronic configuration

1.3.2 describe the number of orbitals making up s, p and d sub-shells, and the number of electrons that can fill s, p and d sub-shells

1.3.3 describe the order of increasing energy of the sub-shells within the first three shells and the 4s and 4p sub-shells

1.3.4 describe the electronic configurations to include the number of electrons in each shell, sub-shell and orbital

1.3.5 explain the electronic configurations in terms of energy of the electrons and inter-electron repulsion

1.3.6 determine the electronic configuration of atoms and ions given the atomic or proton number and charge, using either of the following conventions

1.3.7 understand and use the electrons in boxes notation

1.3.8 describe and sketch the shapes of s and p orbitals describe a free radical as a species with one or more unpaired electrons

1.4.1 define and use the term first ionisation energy, IE

1.4.2 construct equations to represent first, second and subsequent ionisation energies

1.4.3 identify and explain the trends in ionisation energies across a period and down a group of the Periodic Table

1.4.4 identify and explain the variation in successive ionisation energies of an element

1.4.5 understand that ionisation energies are due to the attraction between the nucleus and the outer electron

1.4.6 explain the factors influencing the ionisation energies of elements in terms of nuclear charge, atomic/ionic radius, shielding by inner shells and sub-shells and spin-pair repulsion

1.4.7 deduce the electronic configurations of elements using successive ionisation energy data deduce the position of an element in the Periodic Table using successive ionisation energy data