The answer is that different frequencies of EM waves carry different amounts of energy. The energy of an EM wave depends on its frequency. High-frequency, short-wavelength EM waves have more energy than low-frequency, long-wavelength waves. A high-frequency EM waves carries a lot of energy, so it has the possibility of damaging living tissue. But low-frequency wave carries much less energy, and is safer.
The answer is A, a new chemical substance has to be formed for there to be a chemical change. This is because chemical change happens when a phase of matter changes due to chemicals.
Answer:
d) He, Ar, Kr
Explanation:
To have similar chemical properties, elements must belong to the same period on the periodic table.
As a generally periodic trend, elements within the same group, have the same chemical properties.
So, the correct answer choice will draft elements from the same group.
- He, Ar and Kr belongs to the group of elements called the noble gases.
- They are an unreactive group of elements.
- They are found in the last group on the periodic table.
- These elements do not readily combine with other elements.
