The ionization energy of an atom is the energy required to remove an electron from the atom. In the Bohr model, the ionization energy equals the energy difference between the lowest energy level n = 1 , in which the electron is closest to the nucleus, and the energy level n = [infinity] , which has an infinite radius.

The question is incomplete, the complete question is;

The ionization energy of an atom is the energy required to remove an electron from the atom. In the Bohr model, the ionization energy equals the energy difference between the lowest energy level n = 1 , In which the electron is closest to the nucleus, and the energy level n oo, which has an infinite radius. Compared to the ionization energy of hydrogen, the energy required to remove the electron from singly ionized helium is O two times greater. O four times greater. eight times greater. O one-half as great. O one-fourth as great.

four times greater

Explanation:

For a hydrogen atom, an ionization energy of 13.6 electron volts is required to eject its single electron from the lowest energy level all the way out of the atom.

The helium ground state contains only two 1s electrons. When one of these is removed, He^+ looks quite similar to H^+.

The energy required to remove the remaining helium electron should be; 4×(13.6eV)=54.4eV since the energy depends on the square of the nuclear charge.

-first use of geothermal energy occurred more than 10,000 years ago in north america by american paleo-indians

-the first industrial use of geothermal energy began near pisa, italy in late 18th century

-in 1904, italian scientist piero ginori conti invented the first geothermal electric power plant in which steam was used to generate the power

-with the above experiment, the first geothermal plant in usa started in 1922 with a capacity of 250 kilowatts

-however, in 1946 first ground-source geothermal heat pump installed at commonwealth building in portland, oregon

-during the 1960’s, pacific gas and electric began operation of first large scale geothermal power plant in san francisco, producing 11 megawatts

-in 1973, when oil crisis began many countries began looking for renewable energy sources and by 1980’s geothermal heat pumps (ghp) started gaining popularity in order to reduce heating and cooling costs

-as effect of climate change started showing results, governments of various countries joined hands to fight against it, for which kyoto protocol was signed in japan in 1997, laid out emission targets for rich countries and required that they transfer funds and technology to developing countries, 184 countries have ratified it

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answer;

d. are made mostly of liquid

explanation;

-the general   composition and structure planets includes; they have a thick gas and liquid layer covering a small,solid core. mostly the gases are hydrogen and helium atmosphere and layers of liquid hydrogen. for instance neptune and uranus are examples of the outer planets, they have a core covered by ice and ammonia.

-neptune's atmosphere is hydrogen and helium with a bit of methane so there is no oxygen to breath and the interior is made up of frozen water and ammonia with a rock and iron core. thus, there is no liquid water or solid surface to survive.