No, the atomic number of an element does not change with the loss of an electron. The atomic number of an element is determined by the number of protons in the nucleus of its atoms. It defines the identity of the element and its position in the periodic table.
When an atom loses an electron, it becomes a positively charged ion known as a cation. This occurs when the atom has more protons than electrons, resulting in a net positive charge. However, despite the loss of an electron, the number of protons in the nucleus remains the same, and hence the atomic number does not change.
For example, let's consider the element sodium (Na), which has an atomic number of 11. A neutral sodium atom has 11 protons and 11 electrons. If the atom loses one electron, it becomes a sodium cation (Na+), with 11 protons and 10 electrons. Despite the change in the number of electrons, the atomic number of sodium remains 11.
It's important to note that the mass number of an atom, which is the sum of protons and neutrons in the nucleus, can change if the atom loses or gains neutrons. But the atomic number, determined solely by the number of protons, remains constant for a given element.