A period 4 element is one of the chemical elements in the fourth row (or "period") of the periodic table of the elements.
 The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns.
 The fourth period contains 18 elements, beginning with potassium and ending with krypton.
 As a rule, period 4 elements fill their 4s shells first, then their 3d and 4p shells, in that order; however, there are exceptions, such as chromium.
Harry D. Hubbard was a member of the U.S. Bureau of Standards in the 1920s.
 He modernized Mendeleev's periodic table and in 1924 he produced a Periodic Table of Elements (called the Periodic Chart of the Atoms) which was distributed to schools and universities.
 This version of the periodic table placed the main groups in columns with some later groups taking up two rows per period and the Group VIIIB transition metals displayed out to the right of the noble gases.
 The noble gases themselves were shown first in Column 1 (Valence 0) and repeated in Column 9 (Group VIII).
 The table is also notable for including the solo Neutron as an entry on its own, "above" Hydrogen, and given the symbol lower-case 'n'.
A period 7 element is one of the chemical elements in the seventh row (or "period") of the periodic table of the chemical elements.
 The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns.
 The seventh period contains 32 elements, tied for the most with period 6, beginning with francium and ending with oganesson, the heaviest element currently discovered.
 As a rule, period 7 elements fill their 7s shells first, then their 5f, 6d, and 7p shells, in that order; however, there are exceptions, such as uranium.
A period 6 element is one of the chemical elements in the sixth row (or "period") of the periodic table of the elements, including the lanthanides.
 The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns.
 The sixth period contains 32 elements, tied for the most with period 7, beginning with caesium and ending with radon.
 Lead is currently the last stable element; all subsequent elements are radioactive, however bismuth has a half-life of more than 10 years, more than 1,000 times longer than the current age of the universe.
 As a rule, period 6 elements fill their 6s shells first, then their 4f, 5d, and 6p shells, in that order, however there are exceptions, such as cerium.
A period 1 element is one of the chemical elements in the first row (or period) of the periodic table of the chemical elements.
 The periodic table is laid out in rows to illustrate periodic (recurring) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns.
 The first period contains fewer elements than any other row in the table, with only two: hydrogen and helium.
 This situation can be explained by modern theories of atomic structure.
 In a quantum mechanical description of atomic structure, this period corresponds to the filling of the 1s orbital.
 Period 1 elements obey the duet rule in that they need two electrons to complete their valence shell.
 The maximum number of electrons that these elements can accommodate is two, both in the 1s orbital.
 Therefore, period 1 can have only two elements.
A period 5 element is one of the chemical elements in the fifth row (or "period") of the periodic table of the elements.
 The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns.
 The fifth period contains 18 elements, beginning with rubidium and ending with xenon.
 As a rule, period 5 elements fill their 5s shells first, then their 4d, and 5p shells, in that order; however, there are exceptions, such as rhodium.
Moseley's law is an empirical law concerning the characteristic x-rays that are emitted by atoms.
 The law was discovered and published by the English physicist Henry Moseley in 1913.
 It is historically important in quantitatively justifying the conception of the nuclear model of the atom, with all, or nearly all, positive charges of the atom located in the nucleus, and associated on an integer basis with atomic number.
 Until Moseley's work, "atomic number" was merely an element's place in the periodic table, and was not known to be associated with any measureable physical quantity.
 Moseley was able to show that the frequencies of certain characteristic X-rays emitted from chemical elements are proportional to the square of a number which was close to the element's atomic number; a finding which supported Van den Broek and Bohr's model of the atom in which the atomic number is the same as the number of positive charges in the nucleus of the atom.
 In brief, the law states that the square root of the frequency of the emitted x-ray is proportional to the atomic number.
A period 3 element is one of the chemical elements in the third row (or period) of the periodic table of the chemical elements.
 The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when the periodic table skips a row and a chemical behaviour begins to repeat, meaning that elements with similar behavior fall into the same vertical columns.
 The third period contains eight elements: sodium, magnesium, aluminium, silicon, phosphorus, sulfur, chlorine, and argon.
 The first two, sodium and magnesium, are members of the s-block of the periodic table, while the others are members of the p-block.
 Note that there is a 3d subshell, but it is not filled until period 4, such giving the period table its characteristic shape of "two rows at a time".
 All of the period 3 elements occur in nature and have at least one stable isotope.
Henry Gwyn Jeffreys Moseley (23 November 1887 – 10 August 1915) was an English physicist, whose contribution to the science of physics was the justification from physical laws of the previous empirical and chemical concept of the atomic number.
 This stemmed from his development of Moseley's law in X-ray spectra.
 Moseley's Law justified many concepts in chemistry by sorting the chemical elements of the periodic table of the elements in a logical order based on their physics.
 He published first the Long Form periodic table or Modern periodic table which is used till date.
Dmitri Mendeleev published the first periodic table of the chemical elements in 1869 based on properties which appeared with some regularity as he laid out the elements from lightest to heaviest.
 When Mendeleev proposed his periodic table, he noted gaps in the table, and predicted that as-then-unknown elements existed with properties appropriate to fill those gaps.

Question: What is the birthdate of this English physicist, who published first the Long Form periodic table or Modern periodic table and published Moseley's Law?
Answer: 23 November 1887