Could be lithium (ends with 2s1) or beryllium (2s2)
Lithium
2s
The element with only 3 orbitals is lithium (Li). The electron configuration is 1s^2 2s^1, indicating that it has one electron in the 2s orbital.
Actually the atomic number tells you how many protons there are. And there are 6 elements with 2 electrons. You can find out that out by looking at a periodic table and looking at family 2. Im guessing you won't be able to find the element your looking for unless you know the number of nuetrons or even better the number of protons.
The configuration [He] 2s2 2p2 describes the element in the 2nd row (since He finishes the first row) in the second of the 'p' columns, #14. This corresponds to the element carbon.
The element with the electron configuration 1s2 2s2 2p6 3s1 is sodium (Na).
This chemical element is calcium (Ca).
The element with 2 electrons in the 1s sub-level, 2 electrons in the 2s sub-level, and 2 electrons in the 2p sub-level is carbon (Atomic number: 6).
The full electron configuration for Carbon is 1s^2 2s^2 2p^2. This means that Carbon has 6 electrons distributed in the 1s, 2s, and 2p orbitals.
The element with a valence electron configuration of 2s22p3 is phosphorus (P). This configuration indicates that phosphorus has 5 valence electrons, which are distributed in the 2s and 2p orbitals.
An element cannot have 4 electrons in the 2 s level. The s subshell can hold only TWO electrons. Carbon has 4 electrons in the 2p level, however, if that's what you meant.
4s2 - 9 can be expressed by using the identity: a2 - b2 = (a-b)(a+b) Therefore, 4s2 - 9 = (2s)2 - 32 = (2s-3)(2s+3)