Answer: Hydrogen and Helium
Explanation: Hydrogen is made from from one proton and one electron, making them one of the simplest forms of elements in the universe. Combining hydrogen atoms creates helium, the second most common element in the Universe.
Answer:
All of the above are true
Explanation:
a) The emission spectrum of a particular element is always the same and can be used to identify the element: It's true since the emission spectrum for each element is unique. It has the same bright lines at the same wavelength. This feature is used to identify elements. For example, the study of the emission spectra of light arriving from stars allow us to identify the elements presents in the star because the light contains the emission spectra of those elements.
b)The uncertainty principle states that we can never know both the exact location and speed of an electron: It is true since the velocity of an electron is related to its wave nature, while its position is related to its particle nature and we cannot simultaneously measure electron's position and velocity with precision.
c) An orbital is the volume in which we are most likely to find an electron: An orbital is a probability distribution map that is used to decribe the likely position of an electron in an atom.
<h2>Frequency</h2>
Explanation:
Wave frequency is the number of waves that pass a fixed point in a given amount of time.
Wave speed is the speed at which a wave travels.
Let the wave speed be 
Let the wave frequency be 
Let the wave length be 
The wave speed,frequency and wave length are related by the equation 
.
When increases, increases on the other side to maintain equality when no other property is changing.
Answer:
90° is the measure, hope this helped :)
