下記の英文はアメリカのHighschoolレベルの化学の教材からの抜粋です。灘、開成、桜蔭などの日本のトップ校の生徒なら3分で読解し内容を理解できるはずです。万一、できなかったなら、学校の英語の授業は全く役に立っていない証拠です。
小中高生で、英検１級を持っていても下記の英文を読解できないとするなら、その原因は化学知識がないからです。その人はこの英文の日本語訳を読んでも理解できないでしょう。逆に英語がパッとしない人でも化学知識がある人はこの英文を見て、瞬時に理解できると思います。私は「サイエンスの知識はあるけれども英語力が不十分な小中高生」に英語力をつけるために英文法塾をやっています。
What Are Energy Levels?
Energy levels (also called electron shells) are fixed distances from the nucleus of an atom where electrons may be found. Electrons are tiny, negatively charged particles in an atom that move around the positive nucleus at the center.
Energy levels are a little like the steps of a staircase. You can stand on one step or another but not in between the steps. The same goes for electrons. They can occupy one energy level or another but not the space between energy levels.
The model in the Figure below （クリックすると図が表示されます）shows the first four energy levels of an atom.
Electrons in energy level I (also called energy level K) have the least amount of energy. As you go farther from the nucleus, electrons at higher levels have more energy, and their energy increases by a fixed, discrete amount.
Electrons can jump from a lower to the next higher energy level if they absorb this amount of energy. Conversely, if electrons jump from a higher to a lower energy level, they give off energy, often in the form of light.
This explains the fireworks pictured above. When the fireworks explode, electrons gain energy and jump to higher energy levels. When they jump back to their original energy levels, they release the energy as light. Different atoms have different arrangements of electrons, so they give off light of different colors.