1.what is meant by atomic number of an element?
2.the mass number of an element is 18,it contains 7 electrons.what is the number of protons and neutrons in it?what is the atomic number of the element?
3.an element has an atomic number of 11 and its mass number is 23?what is the arrangement of electrons in the shells? state nuclear composition of an atom of the element?
4.what is the atomic number of an element which has 7 electrons in the M shell?(the K and L shells are completely filled with electrons)?
5.an element has atomic number 13 and atomic mass of 27.(a)how many electrons are there in each atom of the element?(b)how are these electrons distributed in the various energy levels?
6.give the number of protons,neutrons and electrons per atom in the two isotopes of chlorine 17Cl^35 and 17cl^37?
7.what is the reason for the different atomic masses of the isotopes of an element?
I will be happy to critique your thinking on these.
Protons are7 and neutrons are11
1.The atomic number is equal to the number of protons in an atom's nucleus. The atomic number determines which element an atom is.
2. The number of protons and the number of neutrons determine an element's mass number.
(Number of protons + number of neutrons) = mass number. 1 proton= 1 electron.
18 (mass number) - 7 (number of electrons which is equal to the number of protons) = 11 (number of neutrons) .
7 Protons tells us that this element is the 7th element in the periodic table which is Nitrogen.
3. The 11th element in the periodic table is Sodium (Na). Sodium's mass number is technically 22.9898 amu but i guess they rounded it for simplicity.
Sodium has 3 shells.
The first shell (K) has 2 electrons (which for the first shell is complete meaning there are no valence electrons). The second shell (L) has 8 electrons (which for the second shell is complete).
The third shell (M) has 1 electron (the third shell requires 8 electrons to be complete so this means that it has 7 valence electrons).
A valence electron is an electron that is associated with an atom, and that can participate in the formation of a chemical bond; in a single covalent bond, both atoms in the bond contribute one valence electron in order to form a shared pair.
4. The electron shells are labeled K, L, M, N, O, P, and Q; or 1, 2, 3, 4, 5, 6, and 7; going from innermost shell outwards.
Since M is the third shell and it was stated that the K and L shells were completely filled we can add 2 (K) + 8 (L) + 7 (M) = 16 electrons.
16 electrons = 16 protons.
The atomic number is 16.
The 16th element in the periodic table is Sulphur(UK Spelling) or Sulfur (US Spelling)
5.The 13th element in the periodic table is Aluminium which technically has an atomic mass of 26.9815386 amu. Because the atomic number is 13 we know that the number of protons is 13 which means that the number of electrons is 13. Using the K,L,M shells we can determine that Aluminium has completely filled K and L shells and has 3 electrons in the M shell. (13-(2(K shell)+8(L shell))=3
6. An isotope is any of two or more forms of a chemical element, having the same number of protons in the nucleus, or the same atomic number, but having different numbers of neutrons in the nucleus, or different atomic weights.
Number of neutrons = (atomic mass - number of protons)
7. The more neutrons an element has the bigger the atomic mass.
1. The atomic number of an element is the number of protons in the nucleus of an atom of that element. It determines the identity of the element because no two elements can have the same number of protons.
To determine the atomic number of an element, you can look at the periodic table. The periodic table lists all the elements in order of increasing atomic number. For example, the atomic number of hydrogen is 1, while the atomic number of carbon is 6.
2. The mass number of an element is the sum of the number of protons and neutrons in the nucleus of an atom of that element.
Given that the mass number of the element is 18 and it contains 7 electrons, we can deduce the following:
- The number of protons is equal to the number of electrons, which is 7.
- To find the number of neutrons, we subtract the atomic number (7) from the mass number (18): 18 - 7 = 11 neutrons.
- Therefore, the number of protons is 7, the number of neutrons is 11, and the atomic number of the element is also 7 (since the number of protons determines the atomic number).
3. Given that the element has an atomic number of 11 and a mass number of 23, we can determine the arrangement of electrons in the shells and the nuclear composition of an atom of the element.
- The atomic number of 11 means that there are 11 protons in the nucleus of the atom.
- Since the atom is neutral, it will also have 11 electrons.
To determine the arrangement of electrons in the shells, we can follow the electron configuration rules:
- The first shell can hold a maximum of 2 electrons.
- The second shell can hold a maximum of 8 electrons.
- The third shell can hold a maximum of 8 electrons.
So, the electron arrangement in this element would be: 2, 8, 1. This means that the first shell has 2 electrons, the second shell has 8 electrons, and the third shell has 1 electron.
The nuclear composition of an atom of the element would be:
- 11 protons in the nucleus (to match the atomic number)
- 11 neutrons in the nucleus, which can be calculated by subtracting the atomic number from the mass number: 23 - 11 = 12 neutrons.
4. Given that the element has 7 electrons in the M shell, with K and L shells completely filled, we can determine the atomic number of the element.
The electronic configuration of the atom would be:
- K shell: 2 electrons
- L shell: 8 electrons
- M shell: 7 electrons
To find the atomic number, we need to sum up the number of electrons in all the shells:
2 (K shell) + 8 (L shell) + 7 (M shell) = 17
Therefore, the atomic number of the element is 17.
5. Given that the element has an atomic number of 13 and an atomic mass of 27, we can answer the two questions:
(a) The atomic number tells us that the element has 13 electrons because the number of electrons is equal to the atomic number.
(b) To distribute these electrons in the various energy levels, we can follow the electron configuration rules:
- The first shell can hold a maximum of 2 electrons.
- The second shell can hold a maximum of 8 electrons.
- The third shell can hold a maximum of 8 electrons.
So, the electron arrangement in this element would be: 2, 8, 3. This means that the first shell has 2 electrons, the second shell has 8 electrons, and the third shell has 3 electrons.
6. Given the isotopes of chlorine: 17Cl^35 and 17Cl^37, we can determine the number of protons, neutrons, and electrons per atom for each isotope.
- For both isotopes, the atomic number is 17. So, they both have 17 protons.
- The superscript number in each isotope represents the mass number, which is the sum of protons and neutrons.
- For 17Cl^35, the mass number is 35. So, there are 17 protons and 35 - 17 = 18 neutrons.
- For 17Cl^37, the mass number is 37. So, there are 17 protons and 37 - 17 = 20 neutrons.
Since the number of electrons in an atom is equal to the number of protons, both isotopes also have 17 electrons.
To summarize:
- 17Cl^35: 17 protons, 18 neutrons, and 17 electrons per atom.
- 17Cl^37: 17 protons, 20 neutrons, and 17 electrons per atom.
7. The reason for the different atomic masses of isotopes of an element is the variation in the number of neutrons in the nucleus.
Isotopes are different forms of an element that have the same number of protons but different numbers of neutrons. Since the mass number is the sum of protons and neutrons, an isotope with more neutrons will have a higher atomic mass.
For example, carbon has three isotopes: carbon-12, carbon-13, and carbon-14. They all have 6 protons, but their number of neutrons differ:
- Carbon-12 has 6 neutrons.
- Carbon-13 has 7 neutrons.
- Carbon-14 has 8 neutrons.
These variations in neutron numbers result in different atomic masses for each isotope.