Atoms are electrically neutral because they have equal numbers of protons (positively charged) and electrons (negatively charged). If an atom gains or loses one or more electrons, it becomes an ion. If it gains one or more electrons, it now carries a net negative charge, and is thus "anionic."
Waves carry energy from one place to another. Because waves carry energy, some waves are used for communication, eg radio and television waves and mobile telephone signals. ... Some types of waves need to be transmitted through matter, either a solid, liquid or a gas. For example, water waves have to travel in water.
For most healthy adults, the Department of Health and Human Services recommends these exercise guidelines: Aerobic activity. Get at least 150 minutes a week of moderate aerobic activity or 75 minutes a week of vigorous aerobic activity. You also can do a combination of moderate and vigorous activity.
