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Because there are only two elemets whose electrons fill up the first shell of electrons.
Hydrogen: 1 proton, 1 elecrton.
Helium: 2 protons, 2 neutrons, and 2 electrons.
The next on the table, lithium, has 3 electrons, going into the next shell of electrons. The maximum the first shell can hold is two, and helium fills it all, therefore being a stable element and not combining with anything. Hydrogen, on the other hand can combine with elements that have 1 less electron in their last shell. An example of this is oxygen with seven electrons in its last shell. Oxygen creates water with hydrogen.
Wiki User
∙ 12y ago
Wiki User
∙ 13y agoPeriod 1 represents The first atomic shell, which has only one s orbital. The s orbital can hold a maximum of two electrons.
Therefore, you have the first element in Period1, hydrogen, which has 1 electron, and the second, helium, which has 2 electrons.
Wiki User
∙ 10y agoThe first energy level can hold a maximum of two electrons. All but H and HE have more than two electrons. and becuase poo
Wiki User
∙ 11y agoas the first shell can accommodate maximum two electrons therefore first period has two elements.
Wiki User
∙ 11y agoeash shell /orbit had diffrent energy level so in the first shell the energy is n 1x1=n=1.; 1 1=2 if n =2 2x2x2=8
Wiki User
∙ 7y agoOnly hydrogen and helium have only one electrons shell.
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The first period in the periodic table represents elements that possess only the first energy level s orbital therefore this period contains?
Two elements
How many elements in the first period?
Period 1: 2 elements Period 2: 8 elements Period 3: 8 elements Period 4: 18 elements Period 5: 18 elements Period 6: 32 elements Period 7: 25 elements
How many shells do the 4th period elements have?
Every element in the first period has only one orbit. This means that they can have only a duplet in their valence shell, which happens to be their only electronic shell. The elements included in the first period are Hydrogen and Helium.
Why second period elements are called bridge elements?
They are called bridge elements because the 'bridge' the first two elements with only one electron shell to the rest of the Periodic Table, which have ascending amounts of electron shells. The first two are also the most abundant elements in the universe.
How does the Bohr model of the atom relate to the Periodic Table?
The Bohr model of the atom places electrons in orbits or "shells." Elements in the first period only have electrons in the first shell. Elements in the second period have electrons in the first two shells. Elements in the third period have electrons in the first three shells, and so on.
The first period in the periodic table represents elements that possess only the first energy level s orbital therefore this period contains?
Two elements
How many elements in the first period?
Period 1: 2 elements Period 2: 8 elements Period 3: 8 elements Period 4: 18 elements Period 5: 18 elements Period 6: 32 elements Period 7: 25 elements
What elements belong to the first period?
There are two elements in the first period, hydrogen and helium.
The first period in the peroidical table represents elements that possese elements only the first energy level is orbital thefore this perid contains?
two elements, hydrogen and helium.
What is the correlation of a period number with the elements of that period?
all the elements in period 1 have one energy level, all the elements in period 2 have two energy levels, all the elements in period 3 have 3 energy levels... and so on
The first period on the periodic table represents elements that possess only the first energy level s orbital therefore this period contains?
two
How many shells do the 4th period elements have?
Every element in the first period has only one orbit. This means that they can have only a duplet in their valence shell, which happens to be their only electronic shell. The elements included in the first period are Hydrogen and Helium.
Why second period elements are called bridge elements?
They are called bridge elements because the 'bridge' the first two elements with only one electron shell to the rest of the Periodic Table, which have ascending amounts of electron shells. The first two are also the most abundant elements in the universe.
How many elements make up period 1?
Only two: hydrogen and helium. This corresponds to the fact that there can be only two s orbital electrons in any electron shell, and the first shell has only s orbital electrons.
Since the first energy level contains only the 1s sublevel the number of elements in this period is?
2
How does the Bohr model of the atom relate to the Periodic Table?
The Bohr model of the atom places electrons in orbits or "shells." Elements in the first period only have electrons in the first shell. Elements in the second period have electrons in the first two shells. Elements in the third period have electrons in the first three shells, and so on.
How many elements does ammonia has?
There are only two elements. They are hydrogen and nitrogen.
