Alpha particles. Alpha particles are made of 2 protons and 2 neutrons. This means that they have a charge of +2, and a mass of 4. (the mass is measured in atomic mass units, where each proton & neutron=1) We can write them as , or, because they're the same as a helium nucleus, . Alpha particles are relatively slow and heavy.
For more, visit TIME Health. 1  The average attention span for the notoriously ill-focused goldfish is nine seconds, but according to a new study from Microsoft Corp., people now generally lose concentration after eight seconds, highlighting the affects of an increasingly digitalized lifestyle on the brain.
By Kendra Cherry. Updated May 09, 2016. Selective attention is the process of focusing on a particular object in the environment for a certain period of time. Attention is a limited resource, so selective attention allows us to tune out unimportant details and focus on what really matters.