React js css inline style margin right not working

try this: way a)

let styles = {
        marginRight: '20px',
        width: '250px',
        height: '250px',
        backgroundColor: 'yellow',
      };


 <span style={styles} className="badge badge-pill badge-secondary">

way b)

<span style={{margin-right:"20px", width: '250px',height: '250px',background: 'yellow'}} className="badge badge-pill badge-secondary">

React uses camelCase for inline style properties. Try marginRight: '20px', just like you did with backgroundColor.