All officers elected and appointed under this Charter shall before taking their seats or performing any of the duties of their respective offices to which they shall have been elected or appointed, take and subscribe an oath or affirmation that they possess, respectively, the qualifications prescribed by this Charter to hold such office and are not subject to any of the disqualifications prescribed herein; that they will support the constitution of the United States and the constitution of this State, and honestly discharge the duties of the offices to which they are elected or appointed, respectively, to the best of their skill and judgment.
When the officer shall have made such oath in writing and filed the same with the City Clerk, and shall have given the bond required of him, he shall be considered as having qualified for the office to which he was elected or appointed; provided, that if any person so elected or appointed shall not qualify for said office as herein prescribed, within twenty days after he shall have been officially declared elected or appointed thereto, said office shall ipso facto become vacant, and said vacancy shall be filled in the same manner as other vacancies therein are provided for in this Charter.